7: Examination of the Somatic Motor System (Excluding Cranial Nerves)

A. Initial inspection

1. The motor examination begins the instant you meet the patient (Pt). Study every activity: How the Pt sits, stands, walks and gestures; the postures; and the general activity level. Unobtrusive observation of the Pt's spontaneous activity often discloses more than formal tests, particularly in infants or mentally ill Pts.

2. For the formal examination, the Pt undresses and stands under an overhead light. Underclothes remain in place, in deference to modesty, but at some time you must look under them. If you leave one-third of the body covered, you can do only two-thirds of an examination. Before the cock crows, one of you will violate this commandment: thou shalt undress every Pt. Your own anxieties about viewing nudity may exceed those of the Pt about being viewed nude. After all, the Pt came to you expecting an examination.

3. Next, ponder, yes ponder, the Pt's somatotype or body build. Compare the Pt's contours and proportions with those of a standard normal person of like age and sex and with those of family members. From abnormalities in the Pt's Gestalt, sometimes from just a glance at the silhouette, the examiner (Ex) can diagnose an immense number of syndromes, such as arachnodactyly, achondroplastic dwarfism, and Down's syndrome.

4. Next, scrutinize the size and contours of the Pt's muscles, looking for atrophy or hypertrophy, body asymmetry, joint malalignments, fasciculations, tremors, and involuntary movements. Proceed in an orderly, rostrocaudal, face-neck-shoulder-arm-forearm-hand-chest-abdomen-thigh-leg-foot-toe sequence and continually compare right and left sides.

B. Station and gait testing

1. Next, observe the Pt's station, the steadiness and verticality of the standing posture. Then test the gait by asking the Pt to walk freely across the room. Look for unsteadiness, a broad-based gait, and lack of arm swinging. Ask the Pt to walk on the toes, heels, and in tandem (from heel to toe along a straight line). Request a deep knee bend. Ask a child to hop on each foot and to run. Watching the Pt walk is the single most important part of the entire neurologic examination. An essay at the end of Chapter 8 details gait analysis, after you have a better concept of what to look for.

2. Now, rehearse the five steps of Section VI A of the Standard Neurologic Examination (NE). Yes, I'll ask you to demonstrate them by and by.

Note: Do the strength tests on another person. How else can you learn to match your strength against another's?

A. The matching principle

Select those movements that just about match your arm and hand strength. Even if an iron bar loses much of its strength, it may remain too strong for your hands to bend. Conversely, wet tissue paper offers too little resistance. To gauge strength accurately, select movements that are neither too strong for you to possibly overcome nor too weak for you to judge their resistance.

B. The length–strength principle

Under the conditions of clinical testing, the muscles are strongest when acting from their shortest position and have little or no strength when acting from their longest position.

1. To understand the length-strength law, work through Figs. 7-1A to 7-1B to test biceps and triceps strength. You must do the exercises the text calls for. You will find yourself hesitant and clumsy at first—that's why you have to practice, to get a "feel" or sympathy for the task. In all strength tests, the participants should exert maximum power, but they should pull to a peak in a slow crescendo, without jerking.

2. The biceps pull test, biceps against biceps, perfectly exemplifies the matching principle, when the Pt and Ex match muscle to muscle.

3. Relate the strength of the biceps and triceps muscles to their length: these muscles are strongest when acting from their □ shortest/□ intermediate/□ longest position.

   ☑ shortest

4. Now test the flexor and extensor strength of your partner's neck. In testing these movements, place one hand on the Pt's forehead or occiput and the other on the front or back of the Pt's chest to provide bracing and counterpressure.

5. To test the strength of the neck flexors, start with your partner's head strongly extended. Then you resist the neck flexion with your hands. Next test the neck flexor strength when your partner starts with the head tightly flexed, chin on chest. Then you try to extend it. The neck flexors are strongest with the neck □ flexed/ □ extended, in which position the flexor muscles are □ shortest/□ longest.

   ☑flexed; ☑ shortest

6. Next compare the maximum strength of the neck extensors with that of the neck flexors. One action, extension or flexion, by far exceeds the strength of the other. Determine which.

7. To see whether we have discovered a general length-strength law, test the quadriceps femoris and hamstring muscles with the knee fully flexed and then fully extended. With the knee fully extended, the quadriceps femoris muscle is □ strongest/□ weakest and □ shortest/□ longest.

   ☑strongest; ☑ shortest (thus confirming the length-strength law)

   Note: The kinesiologist's length-strength law that the skeletal muscles are strongest when shortest differs from Starling's law of the heart that the output of cardiac contraction increases as the resting length of the cardiac muscle fibers increases.

8. In general, to test muscles of weak or modest strength more accurately, start with the Pt in a position of strength, e.g., neck flexed. But to test very strong muscles, place them at a disadvantage to bring them within your range of strength. Thus, to reduce the strength of the normally powerful triceps muscle to bring it within the testing range, test the Pt with the elbow □ fully bent/□ fully extended. Explain.

   ________________________________________________________________

   ____________________________________

   ☑fully bent

   With the elbow bent, the triceps is longest and therefore weakest.

9. With the elbow extended, the triceps is far too strong for the Ex to overcome. It can lose considerable strength and still offer strong resistance.

C. The antigravity muscle principle: how to remember the strongest sets of muscles

1. Muscles work in opposing, agonist-antagonist pairs (Basmajian, 1985). One of the opposing pairs is immensely stronger than the other, e.g., neck extension is far stronger than flexion. Without a general law to recall the strongest of opposing sets of muscles, you face the oppressive task of memorizing each set individually. If we look at a quadruped, or better, at a man in quadrupedal position, the solution leaps out at us (Fig. 7-2). The immensely powerful muscles all belong to the postural antigravity system of a quadruped.

2. Stand up and assume the postures shown in Figs. 7-2A and 7-2B. Of particular importance, assume the posture shown in Fig. 7-2B. Notice then how the triceps muscle locks the upper extremities against collapse from the pull of gravity and how the quadriceps femoris similarly locks the lower extremities. The neck extensors erect the head. Buttocks and back extensors erect the trunk, holding it from collapse by gravity when the person stands or, equally important, when leaping or locomoting. When a person leaps or locomotes, the hands and feet lever downward. The muscles that support or lock the standing posture against collapse by the pull of gravity and that leap against gravity and propel or locomote constitute the antigravity muscle system. Invariably, the strength of these antigravity muscles greatly exceeds that of their antagonists.

3. Using the principle of the superior strength of the antigravity locking, locomoting, and leaping muscles, predict the strongest of these opposing movements: wrist □ extension/□ flexion; trunk □ extension/□ flexion; foot □ dorsiflexion/□ plantar flexion; toe □ extension/□ flexion.

   ☑ flexion; ☑ extension; ☑ plantar flexion; ☑ flexion

4. Confusion may arise when applying the antigravity theory to some actions such as arm abduction. When abducting, the arm acts against the pull of gravity, but the abductor muscles do not support the standing skeleton against collapse by gravity when the animal stands, leaps, or locomotes; hence, the arm elevators and abductors are not postural antigravity muscles and, quite to the contrary, their opponents are. Consider as examples of postural antigravity muscles the pectoral and latissimus dorsi muscles. The pectoral muscles prevent the forelimbs from straddling out when the animal stands. (Imagine the leverage acting to spread a giraffe's legs.) The latissimus dorsi muscles pull the forelimbs backward, thrusting the shoulders forward and upward, i.e., against gravity, when the quadruped leaps or locomotes. Consequently, the strength of these adductor and flexor muscles acting at the shoulder far exceeds their opponents, the abductor-extensor muscles. Applying this consideration to the hip, which would be stronger? □ hip abductors/□ hip adductors. Explain.

   ________________________________________________________________

   ________________________________

   ☑ hip adductors

   Read the last paragraph again if you can't explain the answer. As another example, consider the action of dorsiflexing and plantar flexing the foot when walking. The dorsiflexors lift the foot against the pull of gravity, but merely act to clear the toes and set the foot in place again so that the powerful plantar flexors can again act to support the posture, leap, or locomote.

5. The antigravity theory predicts not only the strongest muscles but also how much stronger they are. Your arm and hand strength cannot even begin to overcome the antigravity muscles when set in their strongest positions, with fingers, feet, and toes flexed (Fig. 12-13). But your arm and hand strength just about equals or barely overcomes the non-antigravity muscles when set in their strongest position, with the head flexed, jaw open, arms abducted, hips flexed, and wrists and feet dorsiflexed.

6. As a final bonus, the antigravity theory explains the very important posture called decerebrate rigidity, seen in the comatose Pt, when the Pt assumes the position dictated by contraction of the entire system of antigravity muscles (Fig. 12-13).

D. The engagement principle

This is the most commonly neglected technique. For all strength testing and the entire NE, the Ex must engage the Pt's competitive spirit to get maximum effort (Chapter 1, Section IX C 4; DeMyer, 1998). Challenge the Pt to a game: "I am trying to test how strong you are. Do your best on each test. Don't let me win."

A. The rostrocaudal sequence

1. Test the muscles in the natural rostrocaudal order because it requires no memorization. After testing cranial nerve muscles, simply continue in the neck-shoulder-arm-forearm-hand-chest-abdomen-thigh-leg-foot-toe sequence and continually compare right and left sides.

2. Before testing strength, the Ex has an opportunity to test for range of motion of the joints, if the history suggests a need to do so. To test range of motion, ask the Pt to move the joint actively through its full range of motion, and then you attempt to passively manipulate the joint.

B. Testing for weakness of neck flexors and extensors

1. Neck extensors are far too strong for the Ex's arm and hand strength.

2. In what position does the Ex ask the Pt to place the head to bring the strength of the relatively weak neck flexors up into the best range to test?

   ________________________________________________________________.

   Flexion

C. TESTING FOR WEAKNESS OF SHOULDER GIRDLE MUSCLES

1. The trapezius was tested with the cranial nerves (CrNs).

2. Test shoulder and arm movements by having the Pt extend the arms forward, to the sides, and then over the head. Inspect from front and back. Have the Pt stand directly under an overhead light that will cast a shadow of the scapular border. Look for scapular movement, in particular winging of the dorsal border away from the rib cage. Have the Pt lean forward against a wall with the arms extended to exaggerate scapular winging.

3. After testing free movement of arm abduction and elevation, test the strength of these movements. Have your Pt (or partner) hold the arms straight out to the sides (abducted). Push down on the arms as the Pt resists. Where do you push? That depends. If you are a strong man and the Pt a woman, push down proximally at the elbows to reduce your leverage. If you are a woman and the Pt a man, push down distally on the forearms or wrists to increase your leverage. Select a point where your strength in pushing down about equals that of the standard person of the height, weight, age, and sex of your Pt. Here you must build your own catalog of experience. Work through Table 7-1.

4. Arm abduction is complex, requiring supraspinatus action to initiate the act, deltoid action to carry the arm to shoulder height, and scapular rotation to continue the elevation to the vertical position. The serratus anterior and trapezius muscles hold the scapula in place against the chest wall. Serratus anterior paralysis (long thoracic nerve) results in winging of the scapula away from the chest wall.

5. Test for latissimus dorsi strength by starting with the Pt's arms extended to the sides. The Ex applies upward pressure on the elbows. This is a very strong muscle, but it is easily felt and seen. Also, to test for the action of the muscle, the Ex may palpate it while the Pt makes a strong voluntary cough. This test is helpful in Pts with hysterical paralysis of the arm because the action is automatic.

D. Testing for weakness of upper arm muscles: flexion and extension of the elbow

1. Elbow flexors: The Pt tightly flexes the forearm. Brace one hand against the Pt's shoulder. With the other hand, grasp the Pt's wrist and attempt to straighten the Pt's forearm. This matches your biceps against the Pt's. When an average person competes with another average person of the same age and sex, the battle is a deadlock and, hence, ideal for testing (Fig. 7-1A).

2. Elbow extensors: If you give the matter no thought, you might try to test the triceps with the elbow locked in extension. But the triceps, an antigravity muscle, is tremendously strong, and with an average person against another average person, the locked-out elbow wins easily. Conversely, if the Pt's locked-arm yields, the Pt's triceps is significantly weak. For a subtler test, start with the Pt's elbow flexed, as in testing the elbow flexors, but this time grasp the wrist and oppose extension of the forearm by the Pt. This maneuver puts the triceps at a disadvantage, and average person against average person; the Ex will win, but barely. Because this test pits nearly equal strengths, it discloses slight loss of triceps power better than the arm-extended position.

E. Testing for weakness of forearm muscles: wrist flexion and extension

1. Wrist flexors: The Pt makes a fist and holds the wrist flexed against your efforts to extend it. By hooking your fingers around the Pt's fist and flexing your own wrist, you can pit your own wrist flexion against the Pt's. Brace the Pt's wrist with your other hand. Other forms of manual opposition will not overcome the wrist flexors, because they are very strong antigravity muscles. (Visualize a quadruped leaping [Fig. 7-2B].)

2. Wrist extensors: For support, rest the Pt's forearm flat on his thigh or a tabletop. The Pt then holds the wrist forcefully cocked-up (dorsiflexed) as you try to press it down with the butt of your palm on the Pt's knuckles. With the Pt's wrist in extension, the relatively weak wrist extensors just about match your arm and hand strength.

F. Testing for weakness of finger muscles

1. Carefully inspect and palpate the thenar and hypothenar eminences for size and asymmetry. Look for atrophy of interosseous muscles. Elderly people show obvious interosseous atrophy.

2. Abduction-adduction of the fingers: Test by carefully figuring out how to match your strength against the Pt's.

   1. Start with the first dorsal interosseous muscle. Palpate it in your own hand as the mass of soft tissue alongside the second metacarpal bone, in the web between your thumb and index finger. The first dorsal interosseous muscle moves the index finger away from the middle finger and toward the thumb. Palpate your own muscle during that action.

   2. To test a Pt's dorsal interosseous muscle, press the terminal phalanx of your right index finger alongside the resisting terminal phalanx of the Pt's right index finger, matching muscle to muscle, which is an ideal test (Fig. 7-3).

   3. Work through the fingers, learning how to match your finger abductors and adductors against the Pt's.

3. Finger extension: The Pt holds out the hands with palms down and fingers hyperextended. Simply turn your hand over so that the dorsum of your fingernail presses against the dorsum of the Pt's. Then you can carefully match the extensor strength of each of your own fingers against the Pt's.

4. Finger flexion: Strength of the grip as a whole.

   1. Ask the Pt to squeeze your fingers: Grasp the Pt's wrist with one hand to steady the arm and offer two fingers of your other hand for the Pt to grasp. To add an element of fun and competition to the test, particularly with a child, and to keep the Pt working at top strength, say, "Don't let my fingers get away," as you try to extract your fingers from the Pt's grasp.

   2. Try this experiment: Grip a pencil as tightly as possible in your fist. Notice that your wrist automatically dorsiflexes slightly. Have your partner try to pull the pencil out of your grip when your hand is in the normal position it automatically assumes when you tighten your grip. Then hold your wrist flexed as strongly as possible and dorsiflexed as strongly as possible, and ask your partner to pull the pencil out of your grip in each instance. Finger flexion is strongest when the wrist is □ strongly flexed/□ partly dorsiflexed/□ completely dorsiflexed.

      ☑ partly dorsiflexed

   3. This experiment shows that partial dorsiflexion of the wrist allows the strongest grip: Partial dorsiflexion is the functional position of the hand, the position to select when putting a cast on the forearm or wrist to treat a fracture or when splinting the wrist to maintain optimum hand position while the Pt recovers from paralysis. This so-called functional position of the hand is the position of complete shortening of the finger flexor muscles and therefore the position that allows them to exert the strongest grip. Further flexion of the wrist merely slackens the flexor tendons of the fingers without further shortening of the finger flexor muscles. Hence, this action of the hand does not contradict the law that the muscles are strongest from their shortest position. Now if you understand all of this, state into which position you would try to force an assailant's wrist to cause him to drop a knife? Explain.

      _______________________________________________________________

      _______________________________________________________________

      Force the assailant's wrist into flexion. First, your hands have a chance to overpower the assailant's wrist extensors; second, the assailant's flexed wrist can no longer grip the knife strongly, and it may fall out of his hand.

G. Testing for abdominal muscle weakness

1. Position: With the Pt supine (face up), ask for a sit-up or for the Pt to elevate the legs or the head. At the same time, watch the umbilicus as the abdominal muscles contract.

2. Try this experiment: While lying supine, stick your index finger in your own umbilicus to palpate it during the foregoing actions. If the muscles of all four quadrants have equal strength, the umbilicus will remain centered. When the Pt attempts to raise the head or legs, what would happen to the position of the umbilicus if the lower abdominal muscles were weak and the upper muscles were intact? The umbilicus would migrate □ upward/□ downward.

   ☑ upward (the intact muscles pull the umbilicus in their direction)

   1. In general, if some abdominal muscles are weak, the umbilicus will migrate □ toward/□ away from the pull of the intact muscles during strong abdominal contraction.

      ☑ toward

   2. The umbilical migration test aids greatly in localizing the level of spinal cord lesions. The umbilicus corresponds to the X thoracic segment of the spinal cord (Fig. 2-10). Spinal cord transection at the T10 level paralyzes all muscles caudal to that level. Because of paralysis of the lower abdominal muscles, when a Pt with a T10-level cord lesion contracts the abdominal muscles, the umbilicus migrates □ upward/□ downward (Beevor's sign).

      ☑ upward

H. Testing for weakness of the large back muscles

The average Pt's back is far too strong for the Ex to test by manual opposition. Two tests can be done:

1. With the Pt prone, ask the Pt to arch the back and rock on the stomach. Inspect and palpate the paraspinal muscles.

2. Have the Pt bend forward at the waist and straighten up. If you try to oppose the Pt's straightening up from a bent waist, you may cause a back sprain or herniation of an intervertebral disc.

I. Testing for weakness of the hip girdle

1. Hip flexion: With the patient sitting, ask the Pt to lift a knee off of the table surface and to hold the thigh in a flexed position. With the butt of your palm, try to push the knee back down. The flexors are relatively weak, non-antigravity muscles. Give them the advantage of a flexed position.

2. Thigh abduction and adduction: With the Pt sitting, have the Pt hold the legs abducted as you try to press them together with your hands on the lateral sides of the knees. Then have the Pt try to hold the legs adducted (squeezed together) as you place your hands on the medial sides of the knees to try to pull the knees apart. It is inconvenient for the Ex to try to test adductor strength when starting with the Pt's legs apart.

3. Hip extension: With the Pt prone, have the Pt lift the knee from the table surface and hold it up. Place your hand on the popliteal space and try to press the knee back down.

J. Testing for weakness of the thigh muscles

1. Knee extensors

   1. The deep knee bend has already tested the quadriceps, an immensely powerful antigravity muscle that ordinarily is too strong to test by manual opposition if it acts from the strongest position. To test the quadriceps, place it at a mechanical disadvantage, starting with the knee □ flexed/□ intermediate/ □ straight.

      ☑ flexed

   2. With the Pt prone, have the Pt try to touch the heel to the buttock to induce extreme flexion of the knee. Grasp the Pt's ankle and oppose extension. Compare the extensor strength of the two legs.

2. Knee flexors (hamstrings): The Pt holds the knee at an angle of 90 degrees, while you try to straighten it by grasping the Pt's ankle.

K. Testing for weakness of ankle and toe movements

1. Have the Pt dorsiflex, invert, and evert the feet. Inspect, palpate the leg, and check for the strength of these movements by manual opposition.

2. Plantar flexion of the foot is ordinarily too strong to test by manual opposition. Because the Pt walked on the balls of the feet during the gait examination, you already know that the plantar flexors can lift the entire body weight of the Pt.

3. The Pt holds the toes flexed or extended as the Ex attempts to press them back to the neutral position. Which action of the big toe is strongest, □ extension/□ flexion? Explain.

   __________________________________________________________________

   _________________________________

   ☑ flexion

   Of course, flexion! Which action leaps or locomotes and which action merely lifts the foot into place for another leaping or locomoting action (Fig. 7-2)?

L. Screening tests for muscle weakness during the routine physical examination versus a complete examination

1. Testing for weakness of every muscle in every Pt would be a waste of time. For the screening NE, sample a few selected movements, as outlined in Section VI, step C of the Standard NE. Rehearse it.

2. Patients with neurologic symptoms and signs require a much more extensive examination. From the history and initial appraisal, the Ex selects the critical muscles for testing and the conditions under which to do the tests. For example, if the Pt complains of weakness after exertion, have the Pt climb stairs before testing. If the Pt's muscles "freeze up" when cold, put the arm in ice water and ask the Pt to make repetitive contractions. If the muscles cramp when the Pt writes, have the Pt write. Always reproduce any conditions that trigger symptoms.

3. The diagnosis of specific nerve injuries and entrapment neuropathies requires detailed testing of individual muscles and comparison with charts of segmental versus peripheral nerve innervation patterns (Table 2-1 and Figs. 2-10 and 2-11). Of the guides to muscle testing, the little pamphlet entitled Aids to the Examination of the Peripheral Nervous System fits easily in your bag (see also Jenkins, 2002; Sunderland, 1978). For entrapment neuropathies, see Dawson et al. (1998) and Kopell and Thompson (1987).

M. Recording the strength examination

1. Table 2-1 lists muscles or movements usually tested. The Ex may use a word scale, such as paralysis, severe weakness, moderate weakness, minimal weakness, and normal or a numerical scale from 0 to 5 (Table 7-2). Disease-specific gradings are also available (Armon and Ponraj, 1996; Mathieu et al., 2001).

2. A hand-held myometer or dynamometer objectively quantifies strength (Lanska, 2000; Goonetilleke et al., 1994; Thijs et al., 1998; van der Ploeg et al., 1991; Wiles et al., 1990), but remember the principle of full engagement, which states that the Pt's effort is the limiting factor in accuracy.

3. Record in the Pt's chart the movements or muscles actually tested. If the Pt displays weakness on a later visit, the record will provide reliable documentation for comparison.

N. Review

Rehearse Section VI A, B, and C of the Standard NE. Do you remember the steps? No? That's the reason to rehearse them now.

BIBLIOGRAPHY · The Strength Examination

It will not surprise the cognoscente in physical diagnosis that percussion belongs in the sequence of inspection, palpation, and strength testing of muscle.

A. Self-demonstration of percussion irritability of muscle

1. Bare your biceps muscle and strike its belly a sharp blow with the point of your reflex hammer (tomahawk type). You will see a faint dimple or ripple at the percussion site. Strike a crisp blow and jerk the hammer out of the way because the ripple is very transient.

2. The contraction of muscle fibers in response to a direct blow demonstrates the intrinsic irritability of the muscle fibers themselves. It is not a reflex and not dependent on innervation (Brody and Rozear, 1970). In fact, percussion irritability remains, and may even increase, after denervation of the muscle, because the denervated muscle fibers become hyperirritable (Cannon's law of hypersensitivity of denervated structures, Walter Cannon, 1871–1945).

B. Percussion myoedema

Sometimes a tiny hump, called myoedema, appears at the percussion site. The sarcoplasmic reticulum is slow in the reuptake of calcium. Myoedema occurs in some normal people and often in debilitation or dysmetabolic states such as uremia and myxedema.

C. Percussion myotonia

Place your hand, palm up, on the table. Crisply percuss your thenar eminence with the point of your percussion hammer. Normally the thumb bounces up a little due to percussion irritability, but if your thumb slowly rises up from your palm and holds up, you have got problems. You have percussion myotonia.

D. Muscle contraction myotonia

1. Ask the Pt to make a tight fist, hold it for 10 seconds, and flip the fingers open as quickly as possible on command. The myotonic Pt cannot flip the fingers open rapidly, and the wrist involuntarily flexes because of sustained "after contraction" or delayed relaxation of the flexors.

2. Ask the Pt to close the eyelids as tightly as possible for 5 seconds. When the Pt attempts to open the eyelids, the myotonia keeps them closed (Dyken, 1966).

3. Myotonia occurs in myopathies such as myotonia dystrophica (Harper, 2001), myotonia congenita, paramyotonia congenita, certain channelopathies, and in some types of periodic muscular paralysis associated with a disturbance in potassium metabolism (Dubowitz, 1995).

E. Summary of muscle responses to percussion

1. List the three muscular responses to direct percussion: percussion __________________, percussion __________________, and percussion __________________.

   irritability; myoedema; myotonia

2. Normal persons show percussion __________________ of their muscles.

   irritability

3. Some normal persons show percussion __________________.

   myoedema

4. No normal persons show percussion __________________. It indicates a primary disease of the muscle, hence, a myopathy.

   myotonia

5. Apart from the myotonic myopathies, percussion of most myopathic muscles, as in Duchenne's muscular dystrophy, after disease has impaired the contractile properties of muscle, demonstrates little or no contraction. Percussion irritability of muscle is reduced or absent in those myopathies that do not have myotonia, but increases in muscle after denervation.

BIBLIOGRAPHY · Muscle Diseases (Myopathies)

A. Physiology of the muscle stretch reflexes

1. Evolution has perfected muscle fibers as contractile engines. Whatever the stimulus—a nerve impulse, chemical agent, electricity, or mechanical deformation, such as by percussion—the fiber responds by contracting.

2. Stretch of the entire muscle causes reflex contraction of the entire muscle, as contrasted to percussion irritability of individual muscle fibers. The stretch-sensitive receptors for the muscle stretch reflexes (MSRs) are the muscle spindles, which consist of small bags of small muscle fibers (Lance and McLeod, 1981).

   Mnemonic: Remember muscle spindles as "muscles within a muscle" (Fig. 7-4).

3. Effects of stretch on the muscle spindles

   1. The muscle fibers of the spindle originate and insert into the perimysial connective tissue, which ultimately is continuous with the tendons. If the joint shown in Fig. 7-4 extends, the tendon pulls on the perimysium and stretches the muscle spindles. Flexion of the joint causes relaxation of the muscle spindles.

   2. To reset themselves to remain sensitive to stretch throughout the entire range of muscle length, the muscle spindles must readjust their length whenever the muscle length changes.

   3. Flexion of a part momentarily relaxes the spindle tension. The muscle fibers of the spindles respond by contracting slightly to maintain their original tension.

   4. During extension of the part, the spindles adjust to maintain their original tension by lengthening slightly.

4. Innervation of the muscle spindles

   1. Each muscle spindle has its own afferent and efferent axons that maintain its constant tension; see afferent axon A and efferent axon B in Fig. 7-4. The regular muscle fibers, outside the spindle, have only efferent axons, depicted by axon C.

   2. In response to stretch, the spindles send an afferent volley into the neuraxis by axon A. In response to slow stretch, the spindles signal intermittently and asynchronously. The spindles quickly adapt to the new length and resume a baseline level of activity.

   3. If the stretch is rapid, essentially instantaneous, all spindles of the muscle, numbering hundreds, synchronously send a strong afferent volley into the central nervous system (CNS). The strong afferent volley stimulates the lower motor neurons (LMNs) of the regular muscle fibers. The resultant discharge of the LMNs causes a clinically evident muscular contraction, the muscle stretch reflex. Axon C in Fig. 7-4 is the efferent axon.

   4. The event that initiates the MSR is stretch of the □ muscle spindles/□ regular muscle fibers, but the resultant twitch of the entire muscle is the result of contraction of the □ muscles spindles/□ regular muscle fibers.

      ☑ muscle spindles; ☑ regular muscle fibers

5. When the MSR acts, the muscular contraction pulls the two ends of the muscles closer together. The tension on the muscle spindles is momentarily □ reduced/ □ increased. Hence, the spindles cease firing abruptly, and the MSR ends abruptly.

   ☑ reduced

6. When the muscle comes to rest at a new length, what adjustment takes place in the tension of the muscle spindles?

   __________________________________________________________________

   They reset their tension to their baseline level.

7. Explain why only a quick stretch elicits an MSR.

   _________________________________________________________________

   ________________________________

   All spindles must fire rapidly and synchronously to discharge the LMNs. If the stretch is too slow, the spindles fire slowly and asynchronously, and they adapt to the new resting length without sending a sufficiently strong volley to discharge the LMNs.

8. Muscle fibers contract in response to stimulation of the muscle membrane by direct percussion. This phenomenon is called ______________________ irritability of the muscle.

   percussion

9. In contrast to percussion irritability, reflex irritability of muscle depends on a strong volley of afferent impulses initiated by the stretch of the specialized stretch receptors called _______________________________________.

   muscle spindles

10. After interruption of all efferent axons to a muscle, what would be lost, percussion irritability or the MSRs? Explain.

    _________________________________________________________________

    _________________________________________________________________.

    Denervation of a muscle abolishes the MSRs, which depend on the integrity of the reflex arc (Fig. 7-4). Percussion irritability depends on the intrinsic property of muscle fibers. It remains or increases after denervation (Cannon's law of hypersensitivity of denervated end organs).

11. To elicit an MSR and avoid percussion irritability, the Ex stretches the muscles by percussing tendons, not the muscles directly. Direct percussion of the muscle not only causes direct contraction of the muscle fibers but also stretches spindles. The muscle twitches in either case, but clinically the Ex cannot distinguish the cause. The tap on the tendon can elicit contraction only by stretching the muscle spindles.

BIBLIOGRAPHY · Physiology of Muscle Stretch Reflexes

B. Technique for eliciting muscle stretch reflexes

1. Holding the percussion hammer and delivering the blow

   1. A percussion hammer permits you to strike a rapid blow, producing the instantaneous stretch of the muscle spindles necessary to elicit an MSR. To deliver a crisp stimulus, you must learn how to swing a hammer, not peck with it. The same technique applies whether you use the Taylor tomahawk hammer pictured in this text or the long Tromner or Babinski hammer (Lanska, 1999). I prefer the tomahawk-type hammer because hammers with longer handles cannot be used readily on tiny babies in bassinets or threaded easily between the wiring and tubing of a Pt in intensive care. The hammer handle should have convex sides to accommodate the tip of the thumb and forefinger, thus allowing the Ex to hold it loosely to deliver a brisk blow. Hammers with round or octagonal handles, like those given away free by drug companies, will fly out of your hand unless you grip them too tightly, which means you will have to peck rather than percuss.

   2. Hammer pecking is the wrong way to elicit MSRs. Consider first the wrong technique, hammer pecking. The novice grips the hammer tightly with all of the fingers and pecks at the target without using wrist action. Recall how a baby holds a rattle tightly in its fist and bangs or pecks, using all arm action and no wrist action. Grip the handle of your reflex hammer tightly and peck the tabletop in this incorrect manner. (Go ahead, do it. If you know what's wrong, you will appreciate what's right. Pecking is the most common error students make.)

   3. Hammer swinging is the right way to elicit MSRs. Dangle the hammer handle loosely between the thumb and forefinger, allowing it to swing like a pendulum. Think of the hammer handle as a bird: hold it too tightly and you crush it to death; hold it too loosely and it flies away. Figure 7-5 shows how a loose wrist and loose finger grip impart the maximal terminal velocity to the hammer head by literally throwing it without actually releasing it.

      1. Simultaneous extension of the elbow added to the wrist swing adds further velocity to the tip of the hammer, thus delivering the crisp blow that instantaneously and simultaneously stretches all spindles to successfully elicit the MSR.

      2. Practice by holding your wrist a foot above a hard tabletop. Starting with the handle of the hammer lying back across the web between your thumb and forefinger (Fig. 7-5), whiplash the hammer head against the tabletop. If the velocity of the hammer head is great enough and the wrist and grip loose enough, the hammer head bounces all the way back up and falls backward across the crevice between your thumb and forefinger, thus returning to the starting position shown in Fig. 7-5. Practice until you can get this limp-wrist, whiplash feeling of literally throwing or swinging the hammer tip, but without actually releasing the handle. As a loose-wrist hammer swinger, you will proudly elicit MSRs when your tight-fisted colleagues, with their incorrect hammer-pecking style, fail.

2. Eliciting the MSRs in the NE

   1. Have the Pt sit or recline. The Pt places the part to be tested at rest, with the muscles relaxed. Usually the best position is intermediate between full extension and full flexion. The response of the muscle and the mechanics of the tap with the hammer will depend on the joint angle (Lin et al., 1997). About 90 degrees for the elbow, knee, and ankle joints is a standard angle.

   2. Work through Figs. 7-6 to 7-18, testing the reflexes on yourself where possible and on a partner. Do the reflexes in pairs, directly comparing right and left sides.

   3. In testing the knee jerks (quadriceps reflex), have the Pt sit with the legs dangling over the edge of a table. The Ex can then observe the degree of pendulousness, which usually amounts to three after-swings before the leg stops swinging. Normally the foot swings back and forth in an exact straight line. Spasticity diminishes the amplitude and number of after-swings (Fowler et al., 2000) and causes the foot to swing in irregular, rotatory, or sidewise arcs (Wartenberg, 1953).

3. In hypothyroidism, the quadriceps reflex has a "hung-up" appearance when tested with the Pt's legs dangling over table edge. At the end of its extension, the leg appears to pause briefly before dropping into the flexed position. Hung-up reflexes can also be seen in hypothermia, diabetes mellitus, treatment with beta-blockers and complete heart block. Chorea may results in apparently "hung-up" reflexes.

4. The latencies of the MSRs can be recorded by electromyography (EMG) and used in the differential diagnosis of demyelinating and axonal polyneuropathies (van Dijk et al., 1999).

C. What to do if your first attempts to elicit a muscle stretch reflex fail

1. Strike a crisper blow: Make sure you have swung the hammer, not pecked with it.

2. Change the mechanical tension on the muscle: Flex or extend the joint somewhat to alter the tension on the tendon. Compress the tendon slightly more, or slightly less, with your thumb (Fig. 7-7).

3. Try reinforcement

   1. Jendrassik's maneuver for reinforcing an MSR: Slight innervation of the muscle being tested increases the excitability of the LMNs for the MSR. For this purpose, have the Pt make a strong voluntary contraction of a muscle you are not testing. Thus failing to get a quadriceps femoris reflex after several trials, ask the Pt to lock the fingers together and pull hard as you tap the quadriceps tendon (Fig. 7-14). In this, the Jendrassik maneuver, the voluntary upper motor neuron (UMN) innervation of the arm muscles "overflows" to increase the excitability of the LMN pool of the lower extremities (Gasser and Diamantopolous, 1964; Hagbarth et al., 1975; Lance and McLeod, 1981; Stam et al., 1989; Wartenberg, 1945).

   2. The counterpressure method of reinforcement: If Jendrassik's maneuver fails, ask the Pt to tense very slightly the muscle being tested. Ask the Pt to just counterbalance the slight pressure you apply against the action of the muscle, as shown in Fig. 7-15. Too much tension in the muscle keeps the hammer from stretching the muscle spindles.

4. Absence of MSRs: If all maneuvers fail, conclude that the MSRs are absent, which usually indicates a pathologic condition, with some exceptions:

   1. In infants or girls, the lack of prominent tendons may make it difficult to elicit some MSRs, such as the biceps.

   2. Lack of patellar development in infants makes it mechanically difficult to stretch the tendon of the quadriceps femoris muscle by tapping its tendon. Position the infant's leg nearly straight, with the infant recumbent, and then tap the tendon.

   3. During diaschisis or neural shock, such as after acute spinal cord transection, the MSRs may be inactive.

D. Analyze this clinical problem in eliciting muscle stretch reflexes

1. You wish to elicit the biceps reflex of a 38-year-old conscious woman who is seated. Her arm should be positioned _____________________________.

   partly bent across her thigh (Fig. 7-7)

2. If you have struck a crisp blow but noted no MSR, list the maneuvers you must try before concluding that the Pt has no biceps MSR.

   __________________________________________________________________

   __________________________________________________________________

   Change the thumb pressure on the tendon. Reposition the elbow at a slightly different angle. Ask her to "tense" her leg muscles (extend her legs) for reinforcement. (The counterpressure method of reinforcement is inconvenient for arm reflexes.)

3. In the same Pt, you could not elicit the quadriceps and triceps surae MSRs when the Pt was sitting. What maneuvers do you try before concluding she has no quadriceps MSR?

   __________________________________________________________________

   ________________________________

   Above all, strike the tendon a crisp blow. Next, request the Pt to lock her hands and pull as you strike the quadriceps tendon; then ask the Pt to counterbalance the slight pressure you apply against the tibia. These are examples of the pull method (Jendrassik's maneuver) and counterpressure methods of reinforcement.

4. For the triceps surae MSR, use Jendrassik's maneuver and then the counterpressure maneuver by having the Pt slightly plantar flex the foot as you press up on the sole with your finger and tap the Achilles tendon with the other hand. If these maneuvers fail to elicit quadriceps or triceps surae MSRs, place the Pt supine and try different positions of flexion of the legs or have the Pt kneel on a chair.

E. Nomenclature for the muscle stretch reflexes

1. Name the MSRs according to the muscles that respond or to the part that moves, e.g., the quadriceps MSR or the knee jerk (Fig. 7-12), or the triceps surae MSR, or ankle jerk (Fig. 7-16).

2. The fact that tendon percussion elicited the MSR led to the archaic, misleading term of "deep tendon reflexes" for the MSRs. This name implied that the tendons contain the receptor. In fact, the tendon receptors inhibit the MSR. Robert Whytt in 1763 had recognized that stretch was the adequate stimulus for muscle contraction (Pearce, 1997). In 1885, Sir William Gowers (1845–1915) stated:

   • It seems, therefore, most desirable to discard the term "tendon reflex" altogether. The phenomena are, according to the explanation above given, dependent on a "muscle reflex" irritability, which has nothing to do with the "tendon-muscular phenomena," but the intervention of tendons is not necessary for their production; the one condition which all have in common is that passive tension is essential for their occurrence, and they may more conveniently be termed myotatic contractions [myo = muscle; teinein to stretch]. The irritability, on which they depend, is due to and demonstrative of a muscle reflex action which depends on the spinal cord.

3. Gowers synthesized a complex body of knowledge into a single word, myotatic, but his plea for rational, informative terminology has fallen unheeded. Each class of medical students learns about the "deep tendon reflexes" and almost universally fails to understand the spindle mechanism and the adequate stimulus required to elicit the MSRs.

F. Scaling and recording muscle stretch reflexes by using a stick figure

1. Grade the MSRs on a scale of 1 to 4. (Table 7-3) Some Exs require clonus for a score of 4 (Bradley, 1994) but not others (Hallett, 1993; Litvan et al., 1996). Some Exs prefer a verbal description rather than numbers (Manschot et al., 1998).

2. Because of the wide range in normal persons, the absolute value assigned to the MSR is less important than asymmetry, or a discrepancy between one part of the body and another. A stick figure displays the MSRs and, as shown later, other reflexes for interpretation at a glance. Notice in Fig. 7-19A, which shows a normal subject, that the finger and toe flexion MSRs (Figs. 7-10, 7-11, and 7-18) may not be obtainable.

   1. Describe the reflex pattern shown in Fig. 7-19B. ____________________

      Hyperreflexia on the left.

   2. Describe the reflex pattern shown in Fig. 7-19C.

      __________________________________________________________________

      _________________________________.

      Quadriceps hyporeflexia, triceps surae, and toe areflexia on the left.

   3. Describe the reflex pattern shown in Fig. 7-19D.

      _______________________________________________________________

      Areflexia of the left arm.

3. Quantification of the MSRs by use of a mechanical hammer linked to EMG recording may refine the grading and interpretation of subtle reflex differences (Cozens et al., 2000; van Dijk et al., 1999).

BIBLIOGRAPHY · Muscle Stretch Reflexes

A. Areflexia and the reflex arc

1. Areflexia is pathologic, except in toe and finger MSRs and in some particular muscles in infants and females who lack prominent tendons. Some persons with generalized hyporeflexia (or hyperreflexia) merely fall at one end of the normal range. These persons will have muscles of normal size and strength, and sensation will be normal. Ballet dancers and women who wear very high-heeled shoes may lose their quadriceps and triceps surae stretch reflexes (Sadjapour, 1983). In deciphering the cause of areflexia or hyporeflexia, you must think through the afferent and efferent limbs of the reflex arc (Fig. 7-4).

2. To think through a reflex arc, start with the stimulus and the receptor. The adequate stimulus is sudden stretch of the muscle. If you get no response, then ask this question: Was the stimulus adequate? Outline the clinical maneuvers to elicit a reflex when your first attempt fails.

   _________________________________________________________________

   _________________________________________________________________

   Deliver a crisper blow, alter tendon tension by finger pressure or repositioning the part, and try reinforcement.

3. The two methods of reinforcement are:

   1. To have the Pt contract □ strongly/□ weakly a set of muscles not being tested (method of Jendrassik).

      ☑ strongly

   2. To have the patient contract □ strongly/□ weakly the muscle being tested (counterpressure method).

      ☑ weakly

4. Having applied the proper stimulus for the MSR, the next step in thinking through the reflex arc is to consider the integrity of the muscle spindles and afferent limb. We cannot directly check the integrity of the muscle spindle clinically, but we can test the afferent limb as a whole.

   1. Interruption of the nerve or dorsal root conveying spindle afferents would also interrupt other sensory afferents. Hence, areflexia from interruption of the afferent arc causes loss of sensation.

   2. Would interruption of sensory afferents from the muscle cause paralysis? □ Yes/ □ No. Explain.

      _______________________________________________________________

      _______________________________________________________________

      ☑ No

      As long as UMN and LMN pathways to the regular muscle fibers are intact, movement is possible. In tabes dorsalis, for example, the axons of the dorsal roots selectively degenerate. Because the afferent axons from the muscle spindles are lost, the Pt has areflexia and has sensory ataxia but can move.

5. Knowing that the stimulus is proper and that the afferent arc is intact, consider next the LMN and the efferent side of the arc. (We do not consider the synapses of the afferent axon on the LMNs because we cannot evaluate them clinically.) The term LMN includes the cell body of the neuron and its axon. Many diseases attack the bodies of LMNs. Poliomyelitis, one of the most specific, destroys LMNs, with less effect on the dorsal horns or afferent fibers. A Pt with poliomyelitis loses MSRs because of destruction of the efferent arc but retains sensation.

6. After the LMN cell body, consider the efferent axon through the ventral root and peripheral nerve. The efferent axon may be interrupted by mechanical lesions such as cuts or compression. Many toxic and metabolic disorders, such as lead poisoning, may predominantly affect efferent axons, causing a motor neuropathy. Other toxins, such as arsenic, regularly affect afferent and efferent axons, causing a sensorimotor neuropathy. Irrespective of cause and irrespective of involvement of the afferent system, a lesion of the LMN cell body or axons has essentially the same effect on the muscle: weakness, atrophy, and loss of MSRs.

7. Consider next in the efferent arc the neuromyal junction. Two diseases of the neuromyal junction that cause defective impulse transmission are myasthenia gravis and botulism. Myasthenia is a disease of fluctuating intensity. Complete areflexia is unusual. Other major disorders of the neuromuscular junction include Lambert—Eaton myasthenic syndrome (LEMS) and several other congenital (end plate acetylcholinesterase deficiency, acetylcholine receptor deficiency, slow channel syndrome, fast channel syndrome), and several other autoimmune, genetic, toxic and drug related conditions (Conville and Vincent, 2002).

8. The final level of the reflex arc is the effector, the muscle. Many myopathies, including the muscular dystrophies and myositides, may cause areflexia (Karpati et al., 2001; Katirji et al., 2002). The afferent and efferent limbs of the reflex arc are preserved, but the diseased muscle cannot respond.

9. List the clinically significant stations in a reflex arc, beginning with the stimulus.

   _________________________________________________________________

   _________________________________________________________________

   Receptor, afferent axons, LMN (including efferent axon), neuromyal junction, and effector (muscle) (Fig. 2-5).

BIBLIOGRAPHY

B. Effects of neuromuscular disease on muscle size

1. Use hypertrophy and disuse atrophy of normal muscle

   1. The size of normal muscle depends on use. If used, a muscle undergoes use hypertrophy—witness weightlifters. If not used, muscle undergoes disuse atrophy. For example, the muscles of a limb immobilized in a cast begin to undergo disuse atrophy within 24 hours. After removal of the cast, the muscles resume their work, undergo use hypertrophy, and regain their normal size.

   2. UMN lesions that result in paresis or paralysis reduce muscle use. Therefore, the muscles undergo some degree of disuse atrophy, but the atrophy is slight in relation to the effect of LMN lesions or myopathies.

   3. If deprived of axons by LMN lesions, muscle fibers undergo denervation atrophy, a severe atrophy ending in death of the muscle fibers, unless reinnervation occurs.

   4. A normal muscle put at rest for prolonged periods undergoes __________________ atrophy, whereas a muscle deprived of its nerve supply undergoes __________________ atrophy.

      disuse; denervation

2. Myopathies, primary diseases of muscle, also may result in death of muscle fibers. This atrophy is called myopathic atrophy. List the three types of muscular atrophy:

   1. From prolonged inactivity, __________________ atrophy.

   2. From LMN lesions, __________________ atrophy.

   3. From primary diseases of muscle, __________________ atrophy.

      disuse; denervation; myopathic

   4. In some myopathies, notably Duchenne's muscular dystrophy, some muscles go through a stage of pseudohypertrophy, appearing enlarged for the first years before undergoing atrophy.

3. Differentiation of aplasia, hypoplasia, and atrophy

   1. Aplasia (amyoplasia) means that the muscle has failed to develop. Hypoplasia means that the muscle has failed to develop to its normal size.

   2. Atrophy of whatever type (disuse, denervation, or myopathic) means that the muscle once had a normal size and then lost its bulk.

   3. These various terms enable the Ex to designate the mechanism of the reduction in muscle bulk.

4. Circumferential measurement of the extremities: If the history or examination suggests a disorder that could affect muscle size, measure the greatest circumference of the part for documentation in the chart and to compare the right and left sides.

C. Neuromuscular disease, motor units, and electromyography

1. Definition of a motor unit: A motor unit is one LMN, its axon, and all of the muscle fibers it innervates.

   1. Each efferent axon from a motoneuron may innervate one or more muscle fibers. In some small muscles, such as the extraocular, each motor axon is thought to innervate only one muscle fiber. In large muscles, such as the gluteus maximum or quadriceps femoris, each motor axon may innervate hundreds of muscle fibers. Learn Fig. 7-20.

      

   2. If a normal LMN discharges a nerve impulse, □ some/□ all/□ none of the muscle fibers of the motor unit would be expected to contract.

      ☑ all

2. Motor units and fasciculations

   1. The muscle fibers of the motor units are grouped together in a fascicle (fasciculus) of the muscle. If a single motor unit fires, the Ex can see the contraction of the fascicle of muscle fibers as a small ripple or twitch under the Pt's skin. Such a twitch is a fasciculation. You have all probably experienced twitching of an eyelid: that is a fasciculation. The Ex can see fasciculations, and the Pt can see and feel them.

   2. Define a motor unit.

      ______________________________________________________________

      An LMN, its axon, and all the muscle fibers it innervates.

   3. If one motor unit discharges, what would the Ex see and what is the technical name for it? ______________________________________________

      A small muscular twitch called a fasciculation.

3. Myokymia: When motor units discharge abnormally in groups for prolonged periods, they cause a visible, rippling, worm-like action of the muscle called myokymia. The muscles go into more or less continuous spasm that may appear focally or segmentally and may affect at times only the facial muscles or even the ocular muscles. In the "stiff-man" or, better said "stiff-person," syndrome of Isaacs, the myokymia affects widespread muscle groups.

4. Cramps: Cramps are sustained contractions that last seconds to minutes, often brought on by exercise and relieved by stretching the muscle. The EMG shows high-frequency motor unit discharges of 200 to 300 impulses/s.

5. Electromyography

   1. Normally motor units discharge only when stimulated by UMNs or other afferents. A needle inserted into a normal resting muscle and wired to an amplifier and oscilloscope records no electrical activity in most skeletal muscles at rest. When the motor units discharge, the oscilloscope screen displays numerous electrical potentials caused by depolarization of muscle fibers. The recording of this electrical activity from muscle is called electromyography (Aminoff, 1999). See Fig. 7-21.

   2. The surface membrane of a diseased LMN becomes unstable. The neuron may then discharge spontaneous, random impulses, rather than discharging only in response to appropriate stimuli. All the muscle fibers connected to the axon of the motoneuron contract, resulting in spontaneous fasciculations (Fig. 7-21B). Some normal individuals who do not have neuronal disease show benign fasciculations, particularly after exercise.

6. Wallerian degeneration and the EMG of denervation

   1. If the neuronal perikaryon dies, its axon dies. The axon also dies after complete separation from its perikaryon. The process of dissolution of the dead axon and its myelin sheath is called Wallerian degeneration (August Waller, 1816–1870). See Fig. 7-22.

   2. After axonal severance and Wallerian degeneration, the denervated muscle fibers will not contract in response to volition, afferent stimuli, or direct electrical stimulation of the peripheral nerve trunk. The Ex can still elicit a twitch of the denervated muscle fibers by direct percussion until they ultimately die.

7. Fibrillations

   1. Definition: A fibrillation is a random, spontaneous contraction of an individual denervated muscle fiber. After denervation by Wallerian degeneration of the motor axon, the muscle fiber undergoes a period of hyperexcitability (Cannon's law of hypersensitivity of denervated structures). It seems as if the muscle fibers attempt to compensate for the lack of nerve impulses by discharging more easily. Thus, the membrane of the individual muscle fiber depolarizes spontaneously and the fiber contracts. Because of the small size of single muscle fibers, the Ex cannot see fibrillations, but an oscilloscope can record them (Fig. 7-21).

   2. Spontaneous depolarization of the membranes of diseased LMNs causes visible muscular twitches called _______________, whereas spontaneous depolarization of individual denervated muscle fibers causes

      _________________________________.

      fasciculations; fibrillation

   3. The Ex can see the motor unit twitches called ________________, but the oscilloscope is required to "see" the individual muscle fiber contractions called _______________.

      fasciculations; fibrillations

8. After the death of LMNs, fasciculations cease. They occur only during the period when the neurons, although abnormal, remain intact. Fibrillations begin about 3 weeks after denervation and continue for as long as the denervated muscle fibers remain alive, until the final stage of denervation atrophy, when the muscle fibers die.

9. Define fasciculations and fibrillations. Include the operations by which they are detected and their pathophysiology.

   _________________________________________________________________

   __________________________________________________________________

   __________________________________________________________________

   __________________________________________________________________

   Fasciculations are contractions of muscle fascicles, detected by clinical inspection or by characteristic EMG waves. They indicate a hyperexcitable state of the cell membrane of the LMNs, which depolarize spontaneously, causing contraction of all muscle fibers of the motor unit. Fibrillations are spontaneous contractions of individual denervated muscle fibers, detected by characteristic EMG waves. They indicate a state of hyperexcitability of the muscle fibers after denervation.

10. Giant polyphasic motor units: As recorded by EMG, giant polyphasic waves have a greater amplitude and more complex form than do normal motor units (Fig. 7-21). Denervated muscle fibers induce sprouting of new axonal terminals from a neighboring intact axon. When that axon fires, it activates not only its original number of muscle fibers but also the previously denervated adjacent muscle fibers. The larger number of muscle fibers firing causes the polyphasic giant EMG potentials.

11. Magnetic resonance imaging with gadolinium enhancement also provides diagnostic information about denervated and dystrophic muscles (Bendszus and Koltzenburg, 2000).

D. Summary of the clinical and electromyographic syndrome of lower motoneuron lesions

1. The clinical syndrome of LMN lesions consists of paresis or paralysis, atrophy, fasciculations, and areflexia of the affected muscles, summarized in Table 7-7.

2. The EMG syndrome of LMN lesions consists of spontaneous individual motor unit discharges called ______________________, spontaneous contractions of individual muscle fibers called ___________________________, and the appearance of _________________________ motor units on EMG.

   fasciculations; fibrillations; giant polyphasic motor units

BIBLIOGRAPHY · Electromyography and Nerve Conduction Velocity Studies

E. Differentiation of lesions at various sites in the reflex arc

Note: More than one answer may be correct in the next frames.

1. Paresis or paralysis would accompany which one or more of the following? □ dorsal root lesions/□ LMN lesions/□ myopathies

   ☑ LMN lesions and ☑ myopathies

2. Denervation atrophy occurs with which one or more of the following? □ dorsal root lesions/□ LMN lesions/□ myopathies

   ☑ LMN lesions

3. Loss of sensation occurs with which one or more of the following? □ dorsal root lesions/□ LMN lesions/□ myopathies

   ☑ dorsal root lesions

4. Absence of MSRs occurs with which one or more of the following? □ dorsal root lesions/□ LMN lesions/□ myopathies

   all three

5. Complete Table 7-4 to differentiate the various neuromuscular syndromes associated with lesions of the reflex arc. Notice that hypotonia (loose floppy limbs) occurs with lesions at any level of the reflex arc.

1 ☑

2 ☑

1 ☑; ☑2

3 ☑

3 ☑

F. Consider this patient

Three weeks before hospitalization, a 52-year-old man became violently ill with nausea, vomiting, and bloody diarrhea. The gastrointestinal symptoms receded, but 4 days before admission, he began to have severe pain in his extremities and some leg weakness. Examination showed intact cranial nerves. He had slight paresis of his hand muscles and severe leg weakness, most pronounced distally. He was hyporeflexic in the arms and areflexic in the lower extremities. He had difficulty recognizing pinprick and light touch over his hands, and his feet were almost anesthetic. He had no muscular atrophy on admission, but it became evident in 10 days. An EMG on admission disclosed no spontaneous activity indicative of fasciculations or fibrillations. A second EMG, done 3 weeks after hospitalization, disclosed fasciculations and numerous fibrillations in the muscles that were clinically weak and areflexic.

1. This Pt had □ only a motor/□ only a sensory/□ a combined sensorimotor neuropathy.

   ☑ a combined sensorimotor

2. From the history and examination, the evidence for sensory neuropathy was (review the case protocol to sift out the answers):

   __________________________________________________________________.

   symptoms of severe pain, distal sensory loss, and areflexia

3. The evidence for motor neuropathy was ______________________________

   __________________________________________________________________.

   initially, weakness and areflexia; later, atrophy, fasciculations and fibrillations

4. A neuropathy after a severe gastrointestinal upset suggests poisoning. The neuropathy may lag behind the toxic exposure by days or weeks. The Pt's urine had high arsenic levels, the result of rat poison given by his wife.

5. The onset of the Pt's fasciculations and fibrillations 3 weeks after the first clinical signs of neuropathy is the usual time required for these denervation signs to appear. Even if a knife severs a nerve, fibrillations do not appear until 3 or more weeks. Complete Table 7-5.

6. Would a lesion confined to the afferent axons, cause muscular atrophy, fasciculations, and fibrillations? □ Yes □ No. Explain. __________________________

   _________________________________________________________________

   ☑ No. Atrophy, fasciculations, and fibrillations indicate an efferent lesion.

BIBLIOGRAPHY · Arsenic Poisoning

A. Causes of hyperreflexia

1. Hyperreflexia has many causes. Figure 7-23 illustrates that each sign generates many diagnostic possibilities.

2. To analyze any finding, first ask, "Is it merely a normal variation?" Very brisk MSRs may fall within the wide range of normal variation. The most common cause of pathologic hyperreflexia is interruption of UMN pathways between the cerebrum and the LMNs. When UMN lesions increase MSRs on one side, the Ex should also find weakness on that side, i.e., a hemiparesis. The syndrome or pattern of signs integrated with the history produces the diagnosis.

B. Clonus

1. Definition: Clonus is a to-and-fro, 5- to 8-cycles per second (cps), rhythmic oscillation of a body part, elicited by a quick stretch. Clonus is another way to demonstrate hyperactive MSRs after interruption of the UMNs. With extremely brisk MSRs, noxious stimuli and cold elicit clonus (Dimitrijevic et al., 1980).

2. Technique for eliciting clonus

   1. Induce the Pt to relax completely. To elicit ankle clonus, flex the Pt's knee slightly to relax the triceps surae muscle.

   2. Hold the Pt's foot as shown in Fig. 7-24. Gently but briskly jerk the foot upward and a little outward. After the upward jerk, maintain finger pressure against the sole of the Pt's foot. If the foot oscillates between flexion and extension for as long as you maintain pressure, the Pt has the sustained type of clonus.

   3. To elicit wrist clonus, simply jerk quickly up on the Pt's hand.

   4. To elicit patellar clonus, have the Pt's lower extremity straight and relaxed. Grasp the patella between your thumb and index finger and displace it briskly downward in line with the Pt's thigh, stretching the quadriceps femoris muscle. Maintain the downward pressure to sustain the clonus.

3. The mechanism of clonus

   1. The quick dorsiflexion of the Pt's foot stretches the muscle spindles of the triceps surae (Fig. 7-25A). The triceps surae responds with a single MSR, causing the foot to plantar flex (Fig. 7-25B, thick arrow).

   2. The Ex continues to apply light finger pressure against the ball of the Pt's foot throughout. When the plantar flexion stops from the first MSR, the finger pressure immediately dorsiflexes the foot again (Fig. 7-25C, thin arrow). This action elicits another MSR from the triceps surae muscle, and the sequence continues for as long as the Ex maintains finger pressure.

   3. With pathologic hyperreflexia, the Ex can easily sustain the clonus by continued finger pressure.

4. The same technique of applying a quick jerk elicits wrist, finger, or jaw clonus.

5. Explain why the Ex must jerk the part briskly to elicit clonus?

   _________________________________________________________________

   The muscle spindles have to be stretched briskly to initiate an afferent volley.

6. Clinical interpretation of clonus

   1. Some normal individuals with physiologic hyperreflexia will have a few clonic jerks, and this condition is called abortive clonus. In mature individuals, only sustained clonus qualifies as abnormal.

   2. Some normal neonates with extreme physiologic hyperreflexia exhibit sustained clonus set off by movement and gravity (Shuper et al., 1991). It will affect the jaw and the limbs. Simply eliciting an MSR by tendon percussion, jarring the bed, or spontaneous movements of the infant may initiate a train of clonic after-jerks. The proof that the action is clonus comes from immediately arresting it by holding the part to prevent the succession of stretches. Maneuvers of that type do not cause tremors and seizures to stop.

7. Give an operational definition of clonus, i.e., describe the maneuvers and responses.

   _________________________________________________________________

   _________________________________________________________________

   Clonus is a series of to-and-fro rhythmic oscillations of a part generally initiated by a quick jerk that stretches a muscle.

8. Give a pathophysiologic definition of the mechanism and clinical interpretation of sustained clonus.

   _________________________________________________________________

   _________________________________________________________________

   Clonus is a series of repetitive MSRs initiated by stretching the muscle spindles and is indicative of interruption of UMNs (the pyramidal tract).

9. At what age do many normal individuals show clonus? ________________.

   Newborn and young infants

Note: The definition of clonus given here does not apply to the use of the term in describing generalized motor seizures, as in the phrase tonic-clonic seizures. The cause of the to-and-fro movements in seizures is an abnormal hypersynchronous discharge of central neurons, not a perpetuated MSR.

BIBLIOGRAPHY · Clonus

Note: As developed to this point, the syndrome of UMN lesions consists of paresis or paralysis, hyperreflexia, and clonus. Understanding spasticity, yet another component of the full UMN syndrome (Table 7-5), requires a general discussion of muscle tone.

☑ Early

☑ Intermediate

☑ Late

A. Definition

Muscle tone is the muscular resistance that the Ex feels when manipulating a Pt's resting joint (apart from gravity or joint disease).

B. Self-demonstration of muscle tone

1. Place your right forearm across your thigh with your wrist dangling freely. Supinate your forearm to place your radius up. After relaxing this arm completely, grasp its hand with your left hand and flex and extend the wrist as fully as possible.

2. As your active hand moves your relaxed hand, the active hand will feel slight resistance. This slight resistance to passive movement is normal muscle tone. The ligaments set the ultimate range of joint movement.

3. Try now to relax your elbow and, with your other hand, flex and extend your forearm, but now you have to contend with gravity. Try these exercises with a partner.

4. These exercises serve two purposes: to provide proprioceptive experience in judging muscle tone and to provide insight into the difficulty in relaxing a part completely. Do not lose patience when your Pts fail to relax. Keep working patiently to get the part completely relaxed before judging tone.

C. Origin of muscle tone

Normally, the resistance of the muscle to passive movement has two components:

1. The elasticity of the muscle, which ordinarily is slight unless the muscle is fibrotic.

2. The number and rate of motor unit discharges, which is the critical variable. The number and rate of motor unit discharges depend on:

   1. The stimulation of LMNs by muscle spindles and other receptors in skin, tendons, joints, and bone.

   2. Stimulation or inhibition of LMNs by pyramidal and extrapyramidal pathways. Thus muscle tone depends on the activity of motor units as determined by the algebraic sum of diverse excitatory and inhibitory impulses from the peripheral nervous system and CNS on the LMNs.

   3. Because numerous pathways affect tone and the theories about it are complex and conflicting, we will content ourselves with the operational findings and their clinical analysis. We thus avoid the error of giving priority to explanations and interpretations at the expense of operational techniques.

3. You can easily surmise that the two possible alterations of tone are too much tone, hypertonia, and too little tone, hypotonia.

D. Hypertonia

1. The two most common hypertonic states are spasticity and rigidity. Less common is paratonia (Gegenhalten).

2. Spasticity: As operationally defined, spasticity is an initial catch or resistance and then a yielding when the Ex briskly manipulates the Pt's resting extremity. The catch-and-yield sequence resembles pulling the blade of an ordinary pocketknife open. When first opened, the blade resists but quickly yields as it straightens out. The similar phenomenon in muscle tone is called clasp-knife spasticity (Fig. 7-26).

   1. The brisk movement required to elicit clasp-knife spasticity suggests that the stimulus has to engage the muscle spindles. According to this interpretation, the resistance felt is simply an MSR, which then fades out as the muscle spindles readjust. Increased sensitivity of the MSR arc is the fundamental change, of which hyperreflexia, clonus, and spasticity are derivative. Although hyperreflexia, clonus, and clasp-knife spasticity usually parallel each other in intensity, occasionally one feature predominates out of proportion to the others. The pathophysiology of these variations is unknown. Clasp-knife spasticity is generally greater in the flexors of the upper extremities and extensors of the lower.

   2. The three phenomena presented to this point, which indicate a pyramidal tract or UMN lesion and act through an oversensitive MSR arc, are ______________________________________________________________.

      hyperreflexia, clonus, and clasp-knife spasticity

   3. On the assumption that the UMN denervation of the spinal reflex arcs causes spasticity, various therapies have attempted to relieve spasticity by interrupting the arc peripherally and in the spinal cord itself (Goldstein, 2001).

3. Rigidity: As operationally defined, rigidity is an increased muscular resistance felt throughout the entire range of movement when the Ex slowly manipulates a Pt's resting joint. The steady resistance feels like bending solder or a lead pipe. Hence, its name, lead-pipe rigidity. It involves the agonists and antagonists at the joints.

   1. The presence of lead-pipe rigidity indicates an extrapyramidal lesion in the basal motor circuitry, more specifically in the dopaminergic projection from the substantia nigra to the striatum in parkinsonism. The pathophysiology of lead-pipe rigidity is uncertain.

   2. A cogwheel phenomenon often occurs with the rigidity of parkinsonism. The Ex feels the rigidity as a series of ratchet-like catches while slowly moving the elbow or wrist through its range of motion. It apparently reflects the superimposed beats of the parkinsonian tremor, even though the tremor may not be otherwise obvious.

   3. In testing for increased tone, the voluntary movement of a part not under manipulation will increase the tone (Froment's maneuver; Pryse-Phillips, 1995). For example, the Ex asks the Pt to turn the head back and forth while testing tone in the elbow or observing for rest tremor.

4. Paratonia (Gegenhalten: gegen = against or toward; halten = to hold; therefore to hold against or resist).

   1. Definition: Paratonia is the resistance, equal in degree and range, that the Pt presents to each attempt of the Ex to move a part in any direction. It is a pari passu response.

   2. Self-demonstration of paratonia: Press your palms together and, while maintaining the palms in contact with constant slight pressure, move both hands to the right and left and then up and down. Imagine one hand as the Pt's and the other as the Ex's. If one hand increases pressure, speeds up, or detours, so does the other in equal degree. It is like leading and following in ballroom dancing. The balanced, proprioceptive resistance or opposition of one hand in pursuit of another hand is paratonia. The Pt is not necessarily rigid at rest. The Ex feels the paratonia as a slight stiffening of the Pt's limb in response to the contact when the Ex attempts to move the Pt's extremity.

   3. Clinical significance of paratonia: Paratonia occurs in dementia, often in combination with abulia and gait apraxia (Chapter 11). Some otherwise normal persons who cannot relax completely for testing muscle tone show a paratonia-like resistance to passive movement of their parts by the Ex.

E. Review of spasticity and rigidity

1. Give an operational definition of clasp-knife spasticity.

   _________________________________________________________________

   ________________________________

   See frame D 2

2. Give an operational definition of lead-pipe rigidity.

   _________________________________________________________________

   ________________________________

   See frame D 3

3. Clasp-knife spasticity indicates a lesion of the □ pyramidal tract/□ extrapyramidal tracts, whereas lead-pipe rigidity indicates a lesion of the □ pyramidal tract/ □ extrapyramidal tracts.

   ☑ pyramidal tract; ☑ extrapyramidal tracts

4. Check the signs that require a brisk stimulus to elicit.

   1. □ Clasp-knife spasticity

   2. □ Lead-pipe rigidity

   3. □ Hyperactive MSR

   4. □ Clonus

   5. □ Paratonia

      ☑ a; ☑c; and ☑ d

5. Why do the signs checked in frame 4 require a brisk stimulus to elicit them?

   _________________________________________________________________

   _________________________________________________________________

   To activate a strong afferent volley from muscle spindles and to fire the LMNs before the spindles adjust to their new length.

F. Differentiation of spasticity and rigidity

Lesions can affect pyramidal and extrapyramidal pathways, causing mixtures of spasticity and rigidity, especially in cerebral palsy. Usually the Ex can differentiate the two (Table 7-6).

BIBLIOGRAPHY · Spasticity and Rigidity

G. Hypotonia (flaccidity)

1. Definition: Hypotonia is a decreased resistance the Ex feels when manipulating a Pt's resting joint. Hypotonic Pts generally show an increased range of joint movement, as with hyperextensible knees (genu recurvatum) or flaccid heel cords.

2. Causes of hypotonia (Fig. 7-27)

3. Hypotonia from lesions at the level of the reflex arc or peripheral neuro-muscular system. Review Fig. 7-4.

   1. Interruption of afferent fibers in peripheral nerves or dorsal roots reduces muscle tone by removing the inflow of excitatory afferent impulses. In fact, dorsal rhizotomy is done therapeutically in some spastic Pts to reduce muscle tone.

   2. Manifestly, section of ventral roots would cause hypotonia because no nerve impulses could reach the muscles. Primary myopathies cause hypotonia by reducing the ability of the muscles to respond to tonic nerve impulses.

4. Differentiation of peripheral causes for hypotonia: As usual, clinical differentiation depends on fitting the constellation of findings into a syndrome, as outlined in Table 7-4.

5. Central causes of hypotonia (Fig. 7-27): Although cerebral, cerebellar, and brainstem lesions sometimes cause hypotonia, the pathophysiology is elusive. Many congenital brain disorders, such as Down's syndrome and Prader-Willi syndrome, cause profound hypotonia. Patients with spastic cerebral palsy may present as hypotonic infants before spasticity evolves, or they may remain hypotonic.

6. Hypotonia from cerebral or spinal (neural) shock

   1. Definition: Neural shock is a stage of hypotonic total paralysis and total areflexia that immediately follows an acute, severe UMN lesion. Typically Pts with slowly evolving UMN lesions display the standard syndrome of hypertonia, hyperreflexia, and paralysis, in more or less parallel degree. The term shock in this context designates the disastrous disorganization of the acutely injured nervous system. Depending on the lesion site, the Ex may specify cerebral or spinal shock.

   2. Diaschisis: The concept of neural shock of the motor system merges with the general concept of diaschisis. After any acute lesion, the signs and symptoms often exceed what we can understand by the actual tracts interrupted or neurons destroyed. For example, acute, strictly unilateral occipital lobe infarction, may result in complete (bilateral) cortical blindness for a period of hours or days, particularly if the Pt is somewhat obtunded. After that period, the Pt will show only the expected hemianopia dictated by the unilateral destruction of the visual cortex. Constantin von Monakow (1853–1930) named this distant impairment of function, beyond the confines of the acute lesion, diaschisis (Nguyen and Botez, 1998).

   3. Causes of neural shock or diaschisis: Inciting lesions are large, acute, and catastrophic, including trauma, spinal cord transection, and large brain infarcts or hemorrhages.

   4. If a Pt originally in a stage of neural shock begins to recover movement, the recovery usually parallels the emergence of the MSRs, spasticity, and clonus. After most UMN lesions of slow onset, most Pts show increased MSRs, clonus, and spasticity early in the course, without going through a hypotonic phase. Thus, the clinical signs of UMN lesions depend on:

      1. The rapidity of onset.

      2. The size of the lesion.

      3. The stage in the recovery of the CNS after an acute lesion.

H. Testing range of motion

1. The Ex observes the range of motion during the Pt's active free movements of the extremities when testing muscle strength. To test muscle tone, the Pt remains completely relaxed while the Ex moves the Pt's joints slowly through their entire allowable range.

   1. With hyperreflexia and spasticity, the range is reduced. With hypotonia and hyporeflexia or areflexia, it is increased.

   2. Normally you can extend and flex the Pt's wrist to about 90 degrees to the forearm or dorsiflex the foot to nearly a 45-degree angle with the shin.

   3. The range of motion varies with the Pt's age and sex. The newborn infant's foot can be dorsiflexed to contact the shin. Women have slightly more joint excursions than men, and the elderly tend to lose some range of motion.

2. If a joint shows a restricted range of movement, you should continue to apply pressure, taking care not to cause pain. The joint may then yield further.

   1. If it does not yield, it is a fixed contracture.

   2. If it does yield, it is a dynamic contracture.

3. Record range of motion by degrees, using a goniometer or protractor for precision.

BIBLIOGRAPHY · Diaschisis

Note: Do the next part of the text at home to test your own bare foot. Get a reflex hammer and a broken wooden tongue blade to use as stimulating objects.

A. Superficial versus deep reflexes

1. Because stimulation of receptors deep to the skin elicits the MSRs, the MSRs are classed with the deep reflexes. Stimulation of receptors in skin and mucous membranes elicits superficial or skin-muscle reflexes. By stimulating deep or superficial receptors with stimuli of appropriate quality and site (Vlach, 1989), the Ex can elicit a response from each muscle. In addition to causing hyperactive MSRs, spasticity, and clonus, UMN lesions alter the superficial reflexes in characteristic ways.

2. The superficial skin-muscle reflexes commonly elicited in the NE consist of:

   1. Corneal reflex

   2. Gag reflex

   3. Abdominal skin-muscle reflexes

   4. Anal wink and bulbocavernosus reflexes

   5. Plantar reflex (the most important of all reflexes)

B. Standard technique for eliciting the plantar reflex

1. Place the Pt supine with the limbs completely relaxed and symmetrically arranged, and with the knees straight or slightly flexed, with knees slightly turned out. The feet should be warm.

   1. Using the serrated, broken end of a tongue blade, a key, or the butt of a reflex hammer, the Ex strokes the lateral side of the sole (Fig. 7-28).

   2. If the plantar stroke has the correct length, velocity, and pressure, the large toe normally flexes. After UMN interruption, the toe extends at the metatarsophalangeal joint, a phenomenon called the Babinski sign (Joseph Babinski, 1857–1932; Babinski, 1896, 1898; van Gijn, 1996a, 1996b; Fig. 7-33).

2. Because the sole is ticklish or sensitive, the Pt, especially if senile, demented, or paranoid, may view the act of plantar stimulation as unnecessary, ludicrous, or even hostile. Critique each of the following statements and check the statement that best ensures the Pt's relaxation and cooperation.

   1. □ a. "Hold still while I tickle the bottom of your foot."

   2. □ b. "I am going to scratch the bottom of your foot. Hold it still."

   3. □ c. "Hold still while I stimulate your sole."

   4. □ d. "I am going to press gently on your foot. If it's unpleasant, tell me."

      ☑ d

      Statement a ensures that a child or adolescent will giggle and pull the foot away. Statement b will not be welcomed by a Pt who has a burning painful neuropathy or an elderly demented Pt. Statement c uses technical jargon and does not inform the Pt of what you propose to do. Statement d is correct.

3. Next, hold the Pt's ankle with one hand to keep the foot in place and control the pressure of the plantar stroke.

4. Place the stimulus object at the Pt's heel and stroke it slowly along the sole (Fig. 7-28). Make the path along the □ medial margin/□ lateral margin/□ center of the foot.

   ☑ lateral margin

5. Characteristics of the plantar stimulus

   1. Length is only one of the significant variables of the plantar stimulus. Figure 7-28 shows that the plantar stroke stops short of the base of the toes. Extending the stroke to the base of the toes produces unpredictable toe movements.

   2. Another variable is the amount of pressure applied.

   3. A third variable of the plantar stroke is its velocity.

   4. Hence, the three important variables of the plantar stroke are the ______________, _______________, and __________________.

      length; pressure; velocity

6. Self-demonstration of the plantar reflex

   1. Test your own foot and, if available, another person's. Try different velocities, pressures, and lengths, always stopping the stroke short of the base of the toes.

   2. In applying the plantar stimulus to yourself, what errors in the instructions given in B 1 for positioning did you have to make?

      ______________________________________________________________

      ______________________________________________________________

      All of them! You were sitting, your leg was flexed, many of your muscles were contracting, and you had a bent trunk and asymmetrical posture. Reread frame B 1 if you missed this answer.

   3. By stroking your own foot, you will learn to apply the plantar stroke with slight pressure. Patients with sensory neuropathy who have extremely tender soles (hyperesthesia) find the slightest plantar stimulus intolerable. Thus, always begin with very slight pressure or even apply the stroke first to the lateral aspect of the foot (Chaddock's maneuver; Fig. 7-34B), a region less sensitive than the sole.

C. The criterion for success in eliciting a reflex

1. A reflex, by definition, consists of a relatively invariant response to a specified stimulus. Reproducibility is the goal in eliciting any reflex, either toe flexion or extension in the case of the plantar reflex. If no response or inconstant responses occur, your stimulus is probably wrong. Try again.

   1. Consider length first. Having already started at the heel, you can't get much more length and remain on the sole. You must avoid the base of the toes. What remains to increase length is to swing the stroke across the ball of the foot.

   2. If you fail to get reproducible responses after changing the length, change the velocity of the stroke.

   3. If changing the length and velocity of the stroke and using gentle pressure fails, increase the pressure but remain short of pain and within the Pt's limit of tolerance.

2. State the criterion that proves that you have applied the plantar stimulus correctly.

   __________________________________________________________________

   __________________________________________________________________

   Reproducibility of toe movement, either flexion or extension.

D. Summary of the standard method for plantar stimulation

1. Write a statement to forewarn the Pt before a plantar stimulus.

   __________________________________________________________________

   Well, would your statement put you at ease?

2. Describe the correct position of the Pt for the plantar stimulus.

   __________________________________________________________________

   __________________________________________________________________

   Supine, relaxed, all body parts symmetrical, legs extended or knees slightly flexed and turned out, foot relaxed.

3. Why stop the plantar stroke short of the base of toes?

   _________________________________________________________________

   It produces unpredictable toe movements.

4. If you obtain no response or variable responses, what is the most likely explanation?

   __________________________________________________________________

   _________________________________

   The stimulus was improper with respect to length, velocity, or pressure.

E. Anatomy of the plantar reflex arc

1. The reflexogenous zone, the zone from which a reflex can be elicited, is the first sacral dermatome (S1) for the normal plantar reflex. Study the area of the S1 dermatome and its relation to lumbar dermatomes 4 to 5 (L4 to L5) in Fig. 7-29.

2. Cover Fig. 7-29 and shade in the S1 dermatome in Fig. 7-30.

3. Clinical analysis of any reflex requires "thinking through" the reflex arc. According to first principles of thinking through a reflex arc, we begin at the

   _____________________.

   receptor

4. Because the skin contains the receptor nerve endings, the plantar reflex is classed as a □ superficial/□ deep reflex.

   ☑ superficial

5. Learn Fig. 7-31 and then answer frames a to f.

   1. The reflexogenous zone for the plantar reflex is the _______________ dermatome.

      S1

   2. The afferent nerve, or tibial nerve, is a branch of the _______________ nerve.

      sciatic

   3. Mediating the plantar reflex are the IV and V segments of the __________ level of the spinal cord and the I and II segments of the ______________ level.

      lumbar (L4 to L5); sacral (S1 to S2)

   4. The sciatic nerve divides into two large branches just proximal to the knee. The branch to the toe flexors is the _______________ nerve, and the branch to the extensors is the _______________ nerve.

      tibial; peroneal

   5. The major nerve that divides into tibial and peroneal branches is the __________ nerve.

      sciatic

   6. What nerve, if cut, would interrupt the afferent and efferent arcs of the normal plantar response, leaving the toe extensor muscles innervated? _______________

      Tibial

F. Physiology of the plantar stimulus

1. Pain and the plantar reflex: The plantar stimulus results in a somewhat noxious feeling of tickling, pressure, and pain. The effective plantar stimulus presumably acts mainly through the pain receptors in the skin. However, one cannot safely infer from the subjective component of the reflex precisely which receptors elicited the response, because the stimulus activates several types of afferent endings.

2. Summation and the plantar reflex

   1. Figure 7-32 shows the oscilloscopic patterns of electrical shocks applied to a Pt's nerve. The brief shock illustrated in Fig. 7-32A did not elicit a response. Increasing only the duration of the shock elicited a response (Fig. 7-32B).

   2. A stimulus that requires increasing application to elicit a response is said to summate or to undergo summation. A certain minimum number of afferent impulses has to add up, or summate, to fire the LMNs to the muscles. When, as in Fig. 7-32, a stimulus must act over a finite time to cause the reflex, we say that temporal summation has occurred.

   3. Suppose a person fails to feel movement when an object moves a distance of 500 μm across the skin. Then, while keeping the time the same, the Ex moves the object 1000 μm, and the person does feel movement. The response occurs because the object acts on an increased area of skin. This exemplifies □ spatial/□ temporal summation.

      ☑ spatial

3. When the Ex elicits a plantar reflex, the toe may not move until the object reaches the instep or ball of the foot. This delay in the response indicates that some type of summation has occurred.

   1. The fact that moving the object from the heel to the instep requires a finite amount of time suggests that ____________________ summation is necessary.

      temporal

   2. The fact that the moving object stimulated successively more receptors also suggests that ___________________________ summation may have occurred.

      spatial

4. Thus, to get the muscles of the toes to contract, the central excitatory state of the motoneurons was increased by ___________________________ and ___________________ summation.

   temporal; spatial

G. The role of agonist-antagonist contraction in the plantar reflex

1. Reflexes differ greatly regarding the adequate stimulus, the number of muscles acting, and overall complexity. The relatively simple MSR involves a limited muscular contraction. In some reflexes, the simultaneous contraction of the antagonist opposes the prime mover, the agonist. In other reflexes, the contraction of the agonist inhibits the antagonist (Sherrington's law of reciprocal inhibition).

2. In the normal plantar reflex, we know that the toe flexors contract because we can see the toe flex. Occasionally the first response to the plantar stimulus is slight toe flexion that then reverts to extension. The question is whether the toe extensor muscles co-contract in opposition to the flexors and are simply overpowered by the flexors, or whether the toe extensors contract at all. What pathologic conditions or laboratory experiments would prove that the toe extensor and flexor muscles contract simultaneously in the plantar reflex? If you need help to solve the problem, try one of the hints below:

   1. Begin by "thinking through" the reflex arc (Fig. 7-31). Would a lesion, or procaine injected at a particular site, help answer the question?

   2. How would you detect extensor muscle contractions even if the toe moved in the direction of the flexors?

   3. Could you use EMG?

3. Answers to frame 2

   1. The clinically minded investigator would look for Pts in whom the flexor muscles of the toe were paralyzed, leaving the afferent impulses from the sole intact. Such a situation might occur by interruption of the motor branch of the nerve to the flexor muscles, a muscle injury, or by a disease such as anterior poliomyelitis that might happen to destroy the LMNs supplying the flexors, leaving all afferent axons from the sole and efferent axons to the extensors intact.

   2. The laboratory-minded investigator would make simultaneous EMG recordings from the flexors and extensors during the application of the plantar stimulus.

   3. Landau and Clare (1959) concluded from their EMG study that flex-ors and extensors of the toe both contract simultaneously in response to a plantar stimulus, with the outcome a mechanical competition between these muscles, but van Gijn (1976 a & b) disagreed. At the spinal cord level, however, some integrative mechanism must determine whether flexion or extension will occur.

H. Normal variations and flexion synergy in response to a plantar stimulus

1. Flexion synergy

   1. Some normal persons will show little or no toe or leg movement after a plantar stimulus, a so-called mute sole. Arthritic changes, trauma, or previous toes surgery may prevent movement of the toe. Palpate for the action of the extensor hallucis longus tendon, if mechanical factors prevent toe movement.

   2. Most normal persons tend to withdraw their feet from a plantar stimulus and flex the great toe. The withdrawal movement, like the response to stepping on a tack, consists of dorsiflexion of the ankle and flexion of the knee and hip, a triple flexion synergy (Walshe, 1956; van Gijn, 1996a, 1996b). The tensor fasciae latae, hamstrings, and tibialis anterior muscles visibly and palpably contract during this triple flexion synergy. Watch for these actions as you apply the plantar stimulus. Since Babinski's original description, the synergistic extension of the great toe and triple flexion of the ankle, knee, and hip have been considered integral parts of the planter reflex (Babinski, 1896, 1898).

2. The small toes may fan, but this does not constitute a consistent or clinically important part of the plantar reflex.

I. Pathologic variations in the plantar reflexes

1. After interruption of the UMNs to the lumbosacral cord, the great toe extends instead of flexing, a result called an extensor plantar response, extensor toe sign, or Babinski sign (Fig. 7-33A).

2. For best communication, simply state that the Pt has a flexor plantar response or an extensor plantar response, whichever occurred. If you report a Babinski sign, don't redundantly say that the Pt has a positive Babinski sign. There is no negative Babinski sign. The sign, dorsiflexion of the toe, is either present or not.

3. The flexor synergy that tends to withdraw the leg of a normal person after a plantar stimulus usually becomes more prominent and stereotyped in the presence of an extensor toe sign. Although anatomically the upward toe movement is called extension and is mediated by the extensor hallucis longus, physiologically the movement shortens the joint angle and, hence, is regarded as flexion, and the movement belongs to the overall flexion synergy of the leg (Fig. 7-33B).

4. Some Pts voluntarily extend or wiggle the big toe, making the response un-readable. After admonishing the Pt to relax, try again. A struggling child or some Pts with involuntary movement disorders or cerebral palsy may inadvertently or spontaneously dorsiflex the great toe and may hold it tonically extended. To identify a true extensor toe sign, carefully notice the relation of the toe extension and the flexion synergy to the plantar stimulus. A true extensor toe sign meets four criteria:

   1. The toe usually begins to extend only after the plantar stroke has moved a few centimeters along the sole to produce spatial and temporal summations. In some Pts, in particular paraplegics, a very slight or brief stimulus, even a puff or air, may provoke extension.

   2. The toe remains tonically extended as the plantar stroke continues.

   3. Just after release of the stroke, the toe then promptly but slowly returns to the neutral position ("floats" back into neutral position). The mode of return of the toe is as important as the mode of extension in determining the nature of the response.

   4. Some degree of a triple flexion synergy always occurs, best monitored by inspection or palpation of the tensor fascia lata muscle.

5. Thus, the Ex must confirm that the behavior of the toe is indeed related to, provoked by, and dependent on the plantar stimulus, and that any flexion of the leg displays a similar correlation. To qualify as a reflex, the response should show a "machine-like fatality," to use Sherrington's words.

6. Clinicians interpret the extensor toe response as a sign of anatomic or pathophysiologic interruption of the pyramidal tract (van Gijn, 1996a, 1996b; Walshe, 1956). No other hypothesis fits the facts as well. Reversible pathophysiologic conditions that result in transient extensor toe signs, with or without the other features of the UMN syndrome, include toxic-metabolic coma, postictal hemiparesis after epileptic seizures (Todd's paralysis), trauma with concussion or contusion, transient ischemic attacks, and hemiplegic migraine. The Pt's prompt and full recovery provides the proof of a transient pathophysiologic state rather than anatomic interruption of the pyramidal pathway (Walshe, 1956).

J. Plantar responses in infants

1. Observers differ as to the frequency of the extensor response in young infants. Examine the infant supine, awake but not crying, and with the head in the midline. In normal young infants, the toe response varies, depending on the qualities of the stimulus. When you next examine a young infant, apply a very light stroke with the tip of your fingernail, merely a caress. The toe extends. Then, with the pad of your thumb (not the nail), apply pressure on the ball of the foot. The toe flexes. Neither stimulus will cause any discomfort. The thumb pressure will cause a plantar grasp reflex that competes with toe extension. Then apply a standard plantar stimulus. The response elicited, extension or flexion, depends in large degree on the nature of the stimulus imposed, whether nociceptive, a simple touch or pressure, and the object used to apply the stimulus (Bodensteiner, 1992).

2. Hence, the extension of the great toe, although pathologic in older Pts, does not indicate that the young infant has a UMN lesion. In general, the closer the Pt's age to 1 year, the more constant the flexor response (Zafeiriou et al., 1999).

3. By including the test for the plantar grasp reflex, the Ex adds significant information. It should be active and demonstrable in normal infants. Its absence in the first 6 months correlates with poor neurologic development (Futagi et al., 1999).

4. Contrast the clinical significance of an extensor toe response in infants and older subjects.

   __________________________________________________________________

   __________________________________________________________________

   Normal infants variably show extensor or flexor toe responses, depending on the nature of the stimulus. In older persons, consistent extensor responses indicate a UMN lesion.

K. Changes in the stimulus and reflexogenous zone for the plantar reflex after upper motoneuron lesions

1. To elicit a plantar response requires a combination of site, length, velocity, and pressure of the stimulus. The usual reflexogenous zone for a plantar reflex, either normal or pathologic, is the ___________ dermatome. Draw a foot, shade this dermatome, and check it against Fig. 7-29.

   S1

2. After severe structural lesions, such as complete spinal cord transection, the extensor toe sign and leg withdrawal lose all local signature or local specificity. Almost any stimulus of any part of the skin caudal to the level of the lesion results in toe extension, with a strong flexor synergy or flexor spasms.

3. Additional maneuvers for eliciting superficial toe reflexes

   1. Many other eponymic maneuvers besides Babinski's elicit toe movement from superficial stimuli (Ghosh and Pradhan, 1998; van Gijn, 1996b). These maneuvers, in particular those outside the S1 dermatome, generally are less effective than stimuli within the S1 dermatome. In normal persons, these stimuli usually fail to elicit toe flexion, but after UMN lesions, they may elicit toe extension, just as with Babinski's maneuver (Fig. 7-33). Ghosh and Pradhan (1998) found that the maneuver of Gonda (Fig. 7-34G) elicits toe extensions more readily than planter stimulation in children with spastic cerebral palsy.

   2. The multitude of eponyms implies that the maneuvers represent different phenomena, but physiologically, as stimuli, the maneuvers betray a unifying simplicity. Do the maneuvers shown in Fig. 7-34 on yourself and a partner, paying attention to the stimulus properties of each maneuver.

   3. Can you recognize the common physiologic features of the stimuli used in Fig. 7-34?

      _______________________________________________________________

      _______________________________________________________________

      _______________________________________________________________

      In each maneuver, the stimulus acts over a certain interval of time, stimulates more than one point of skin, and causes a noxious or uncomfortable sensation. We can infer that these maneuvers act through a spatially and temporally summated, somewhat noxious superficial stimulus to elicit the plantar response (Roby-Brami et al., 1989).

   4. You can now discover new signs yourself. Run your thumbnail down your shin: You have now discovered a new sign. Squeeze on a corn (a very effective way to elicit an extensor toe response) and you have another sign, and so on. The response from the S1 dermatome is the most constant and useful. If stimulation of the S1 dermatome produces a convincing, reproducible response, the other maneuvers are superfluous. Sometimes, after an equivocal response to plantar stimulation, doing another maneuver, such as Oppenheim's or Gordon's, simultaneously with the plantar stimulus may enhance toe dorsiflexion.

   5. If you want to know all the eponyms to feel educated, try the following mnemonic.

Mnemonic: Eponymic ways to produce an extensor toe sign (Fig. 7-34):

• B is for Babinski, stimulate the bottom of the foot.

• C is for Chaddock, stimulate the lateral side of the foot.

• G is for Gonda, grasp the IV digit.

• Go is for Gordon, grip the calf.

• O is for Oppenheim on the shin maneuver.

• S is for Schaeffer, squeeze the Achilles tendon.

BIBLIOGRAPHY · Extensor Toe Sign and Plantar Responses

L. Reasons for the otherwise puzzling absence of extensor toe signs in patients with upper motoneuron lesions, or how to avoid being fooled

1. Analysis of a Pt

   A 24-year-old man struck his head on the bottom of a swimming pool when he dove in. The impact forced his head sharply backward. Examination shortly after his neck injury disclosed complete paralysis, absence of all superficial and deep reflexes, and complete anesthesia caudal to C5. Breathing was solely diaphragmatic.

   1. Such a phase of complete paralysis, hypotonia, and areflexia after an acute, severe spinal cord injury is called _____________ shock.

      spinal (or neural)

   2. Within 8 days, his MSRs returned and became very hyperactive. Extensor toe signs appeared and sensation started to return. Within 15 days after injury, the full UMN syndrome was present, but some weak voluntary movements had returned. Eight weeks after the injury, he was able to move all extremities. Six months after the injury, he had slight hyperreflexia of the left leg and a suggestive extensor toe sign on the left, but otherwise walked fairly normally.

   3. A contusion of the Pt's spinal cord had temporarily interrupted all impulse transmission through the lesion site. After recovery, he still had residual signs indicating permanent destruction of some UMN axons on the left side of the cord.

      d. Thus one reason for absence of an extensor toe sign after UMN lesions is the stage of spinal or cerebral (neural) shock.

2. Compression damage to the common peroneal nerve

   1. Compression neuropathy of the common peroneal nerve may account for absence of a Babinski sign by interrupting the innervation of the toe extensor muscles. Patients paralyzed from any cause, UMN or LMN, may suffer from compression damage to the common peroneal nerve because the paralyzed leg may rest in outward rotation, in the same position, for long periods. The nerve then gets compressed between the fibular head and the bed surface or bed rail (Fig. 7-35).

   2. Feel the head of your fibula. Move your fingertip a half a centimeter or so distally. To feel your common peroneal nerve, press fairly hard and move your fingertip back and forth across the fibula. Because the nerve angles obliquely downward and forward across the fibula (Fig. 7-35), you should feel it slip back and forth under your fingertip.

3. Common peroneal palsy and foot drop

   1. The common peroneal nerve warps around the fibular head and passes into the "fibular tunnel" (between the peroneus longus muscle and the fibula). Damage to the common peroneal nerve causes a foot drop because it supplies all foot and toe extensors. The Pt cannot dorsiflex the foot and toes, and the toes will drag when the Pt walks. If the Pt recovers from UMN paralysis, such a remaining peroneal palsy precludes a satisfactory gait. The physician has to ensure proper measures to protect the peroneal nerve, ulnar nerve, and other nerves of paralyzed Pts and when applying casts for fractures.

   2. Crossed knee peroneal palsy: The superficial position of the nerve accounts for a common cause of foot drop, the so-called crossed knee palsy. The Pt compresses the nerve when sitting with one knee crossed over the other. Cross your legs and notice how the peroneal nerve may be entrapped between the fibula and the patella and lateral condyle of the opposite knee.

4. Give two basically different reasons for the absence of an extensor toe sign after an undoubted UMN lesion.

   __________________________________________________________________

   __________________________________________________________________

   Spinal or cerebral shock; a lesion of the reflex arc, such as peroneal nerve injury; loss of afferent impulses from sensory neuropathy; etc.

5. Even after exclusion of all of the foregoing explanations, some Pts with UMN lesions will fail to show an extensor toe sign or other features of the UMN syndrome. Then we have to invoke "biologic variability" but do so only after careful analysis of all the possible pathogenic factors.

BIBLIOGRAPHY · Peroneal Neuropathy

M. Technique for eliciting the superficial abdominal and cremasteric reflexes

1. Stroking the skin of the abdominal quadrants or inner thighs elicits the superficial abdominal and cremasteric reflexes (Fig. 7-36).

2. Using a broken tongue blade, a key, or the blunt end of a reflex hammer, practice obtaining the superficial abdominal reflexes on yourself and a partner. In contrast to the plantar reflex, the stimulus may have to move a little faster, almost a whisk action of the wrist, to elicit the twitch of the umbilicus toward the quadrant stimulated. The partner may sit or recline. You may be unable to obtain the reflex on yourself, but by trying, you will learn two important things:

   1. The stimulus is somewhat unpleasant.

   2. Excessive tension in the abdominal muscles obscures the abdominal skin-muscle reflexes. Because you will have to flex or raise your head, you may tense your muscles too much. However, slight abdominal tension may reinforce the response.

3. Normally in response to abdominal skin stimulation, the umbilicus twitches □ toward/□ away from the quadrant stimulated.

   ☑ toward

4. Normally in response to thigh stimulation of a male, □ elevation/□ depression of the □ ipsilateral/□ contralateral/□ both testicle(s) occurs. Females, of course, do not exhibit this reflex.

   ☑ elevation; ☑ ipsilateral

5. The abdominal stimulus has the same properties as the plantar stimulus. If perceived by the Pt, the stimulus is felt as _______________, and it requires ______________ and ______________________ summation.

   unpleasant (noxious); spatial; temporal

6. Therefore, in deference to the Pt's comfort, apply the first abdominal stimulus gently.

7. Effect of UMN lesions on the abdominal and cremasteric reflexes: These superficial reflexes disappear, at least temporarily, after UMN lesions.

8. Natural history of the abdominal and cremasteric reflexes

   1. You may find it difficult to elicit abdominal reflexes in normal young infants. The individual, whether infant or adult, has to relax to tolerate the somewhat uncomfortable or tickling sensation produced. Abdominal tension obscures the response. As the infant matures, the abdominal reflexes appear.

   2. In normal elderly or obese Pts or in multiparous women with lax abdomens, the abdominal reflex is often absent.

   3. In the acute phase of an UMN lesion, the abdominal and cremasteric reflexes are usually absent. Later they may recover. If the brain lesion occurs early in life, as in cerebral palsy, these reflexes regularly return.

9. What two normal features of the superficial reflexes in young infants would indicate UMN interruption in a more mature patient?

   _________________________________________________________________

   Extensor toe responses and absence of abdominal reflexes.

N. Anal wink (S2, S3, S4) and bulbocavernosus reflexes (S3, S4)

1. Pricking the skin around the anus causes a quick, twitch-like constriction of the anal sphincter, the so-called anal wink. The anal reflex is the first spinal reflex to return after spinal shock (Pedersen et al., 1978).

2. Pricking the glans penis causes reflex contraction of the bulbocavernosus muscle, detected by pressing a (gloved) finger against the Pt's perineum. The pinprick may also elicit an anal wink.

3. Perform these tests to investigate symptoms such as incontinence or impotence that suggest a lesion of the lumbosacral cord, cauda equina, or lumbosacral plexus, not as part of the routine NE. EMG studies of the anal sphincter and anal wink reflex are also helpful (Pedersen et al., 1978).

BIBLIOGRAPHY · Anal Reflexes

O. Recording the reflexes

1. A stick figure conveniently displays several routinely elicited reflexes (Fig. 7-37). Record the MSRs as 0 to 4+; the toe response with an up or down arrow; the abdominal and cremasteric reflexes with a 0 if absent, ± if equivocal or barely present, and + if normally active.

2. Figure 7-37 A depicts □ hemiplegia/□ quadriplegia/□ paraplegia.

   ☑ hemiplegia

3. Figure 7-37B depicts □ hemiplegia/□ quadriplegia/□ paraplegia.

   ☑ quadriplegia

4. Patient analysis: Consider a paraplegic Pt with spinal cord transection at the X thoracic level. The IX and X thoracic segments innervate the upper half of the abdomen, the XI and XII the lower. Thus the UMN signs appear only distal to T10. Fill in Fig. 7-37C to show the reflex pattern expected.

5. What direction would the Pt's umbilicus in Fig. 7-37C move if he were supine and attempted to elevate his head and shoulders? Explain.

   __________________________________________________________________

   __________________________________________________________________

   The umbilicus would migrate upward (Beevor's sign) because the rectus muscles of the upper part of the abdomen would contract, but the muscles of the lower abdomen would be paralyzed.

6. The Ex can also use the MSR of the abdominal muscles to localize a lesion at T10. Place a finger in each of the four quadrants and tap it briskly, as in eliciting the brachioradialis reflex (Fig. 7-9). The hyperactive response from the two lower quadrants will contrast with the normal or negligible response from the upper two quadrants.

A. Complete Table 7-7 to contrast the typical findings with a chronic upper motoneuron lesion and a chronic lower motoneuron lesion.

B. Clinical variations in the pyramidal (upper motoneuron) syndrome

The level of the lesion along the course of the pyramidal tract (Fig. 2-29) determines the distribution of the weakness and other UMN signs. For the effect on the gait, see the gait essay at the end of Chapter 8.

1. Standard hemiplegic distribution: Unilateral interruption of the pyramidal tract at any level from the cortex to the pontomedullary junction causes weakness of the contralateral side of the body, from the lower facial muscles on down (Fig. 6-8B).

   1. The degree of paralysis depends on how many of the million or so axons of the pyramidal tract (DeMyer, 1959) the lesion interrupts, and the individual variation in the number of crossed and uncrossed axons.

   2. The gradient and distribution of weakness are highly characteristic, essentially pathognomonic, of pyramidal tract interruption at cerebral, midbrain, and pontine levels. The weakness or paralysis involves the contralateral lower facial muscles and the contralateral extremities. Medullary level lesions usually spare the face. In the extremities, the distal muscles are more affected than the proximal, and the finger movements suffer most of all. Unilateral paralysis of the tongue, palate, pharynx, and larynx is unusual, but the ipsilateral sternocleidomastoid is affected (Chapter 6). The opposite hemidiaphragm is weak during volitional breathing but acts bilaterally during automatic breathing (Chapter 6). UMN interruption equally paralyzes flexor and extensor muscles, contrary to traditional opinion (Thijs et al., 1998).

2. Monoplegia: A small lesion of the motor cortex or internal capsule, where the pyramidal fibers have a discrete somatotopic arrangement, may cause contralateral weakness of one arm or one leg or, rarely, just one or a few finger movements (Kim, 2002; Takahashi et al., 2002). A lesion of the leg area of its projection fibers will cause a contralateral lower extremity monoplegia. Interruption of the pyramidal tract on one side of the thoracic spinal cord causes a monoplegia of the ipsilateral leg.

3. Double hemiplegia: The lesion interrupts both pyramidal tracts somewhere rostral to the pontomedullary junction. The lower part of the face and all four extremities are paralyzed bilaterally. The Pt also shows pseudobulbar palsy.

4. Spastic diplegia: Bilateral pre- or perinatal cerebral lesions may result in a bilateral pyramidal syndrome, but with the legs more affected than the arms, and the bulbar muscles relatively spared. This reverses the arm-leg gradient of the weakness of double hemiplegia. Spastic diplegics often display involuntary movements such as athetosis.

5. Pseudobulbar palsy: Bilateral interruption of the corticobulbar component of the pyramidal tract (or all of the tract, at cerebral or brainstem levels) causes bilateral weakness of the oropharyngeal muscles with dysphagia, dysarthria, and spastic dysphonia, but the Pt shows exaggerated smiling and crying (Chapter 6).

6. Locked-in syndrome: Bilateral interruption of the pyramidal tracts in the basis pontis or cerebral peduncles causes UMN paralysis of all volitional movements except vertical eye movements. The Pts remain conscious and not demented but are "locked-in" to themselves by the paralysis. See Chapter 12.

7. Quadriplegia (tetraplegia): Bilateral interruption of the pyramidal tracts in the caudal medulla or cervical region spares the face but paralyzes the volitional movements of the trunk and all four extremities. The Pt loses volitional bladder and bowel control and volitional control of breathing. The lesion spares those corticobulbar fibers to the face and bulbar muscles that depart rostral to the medullary level (Chokroverty et al., 1975; Ropper et al., 1979).

8. Paraplegia: Bilateral interruption of the pyramidal tracts caudal to the cervical region spares the arms but causes paralysis of the legs, with loss of bladder and bowel control.

C. A warning about the presence or absence of muscle stretch reflexes in relation to upper and lower motoneuron lesions

1. Although the general rule that LMN lesions cause hyporeflexia or areflexia and UMN lesions cause hyperreflexia holds, you now know that, in the acute phase of UMN lesions, the MSRs may be temporarily absent.

2. In the Guillain-Barré (Landry-Guillain-Barré-Strohl) syndrome of polyneuropathy, the Pt typically suffers an ascending flaccid paralysis, beginning in the lower extremities. Typically also the Pt has the expected areflexia. In some Pts with the axonal form of this neuropathy, the MSRs are preserved or even hyperactive (Yuki and Hirata, 1998). Thus the distinction between a central or peripheral paralysis, that is, between a neuropathy and a myelopathy, becomes difficult on clinical grounds alone. The EMG aids materially in the differential diagnosis by placing the lesion in the peripheral nervous system and in differentiating the demyelinating from axonal forms of the syndrome (Van Dijk et al., 1999).

D. Review of paralysis and sensory deficits immediately after acute spinal cord transection

1. Spinal cord transection at the medullocervical junction or at segments C1 to C3 (Fig. 2-5) results in complete apnea, complete quadriplegia, and complete anesthesia caudal to the lesion. The Pt dies of hypoxia within minutes unless given artificial respiration. The blood pressure also drops because interruption of the reticulospinal tracts stops the down flow of vasoconstrictor tone to the preganglionic sympathetic neurons in the intermediolateral column of the spinal cord. The sensorimotor deficits affect only the trunk and legs if the lesion is caudal to T1 (paraplegia).

2. During the stage of spinal shock, the Pt loses all somatomotor and most visceromotor responses caudal to the level of the lesion. The Pt shows flaccid paralysis of somatic muscles and sphincters and flaccid (atonic) bladder and bowel paralysis, with incontinence. All superficial and deep reflexes and most autonomic reflexes are abolished. If any visceral-related function remains, it is usually anal sphincter tone.

3. Gradually the classic UMN signs of increased MSRs, spasticity, and extensor toe signs will appear, as will reflex emptying of the bladder and bowel. In contrast, slowly evolving spinal cord compression results in spastic paralysis from the start. The Pt does not go through a phase of spinal shock.

4. After the phase of spinal shock, the transected spinal cord, isolated from the brain, can mediate simple actions such as MSRs and flexor withdrawal reflexes. It can also mediate reflex sweating, piloerection, micturition, defecation, and ejaculation (although the Pt feels no sensation), but it cannot produce any voluntary movements, respiratory drive, or respiratory-related reflexes such as coughing, sneezing, and hiccoughing. These reflexes require coordination of bulbar and spinal muscles. In summary, the isolated spinal cord can reflexly twitch some muscles, sweat, ejaculate and reflexly eliminate urine and feces, but the isolated spinal cord cannot breathe or make voluntary movements. These actions require intact reticulospinal and corticospinal tracts from the brain.

E. Patient analysis

1. Medical history: This 61-year-old man awakened one morning with double vision and inability to move his right side. He noticed mild numbness and tingling of his right side. When he called to his wife, he noticed slurring of his speech. He had been diabetic and hypertensive for many years.

2. Physical findings: The Pt was conscious, cooperative, and intact mentally. His left eye turned down and out, and the pupil was dilated. He could not adduct it. He had mild dysarthria. He had severe weakness of the right extremities, including the lower part of his face on the right. His right extremities were flaccid and somewhat hyporeflexic. He had a flexor plantar response on the left but little response at all on the right. He responded somewhat less to pain and touch on the right side.

3. Lesion localization

   1. Before continuing with the text, you may want to propose where and what the lesion is. It may help you to review the brainstem cross sections shown in Figs. 2-15 to 2-18.

   2. In localizing a single lesion to explain the Pt's findings, first assemble the data that require explanation. The flaccidity and weakness, in a hemiplegic distribution, indicates interruption of the pyramidal tract in the acute stage of shock. The slight sensory findings suggest some involvement of a sensory pathway. The pupillodilation, down and out position of the left eye, and inability to adduct it indicates a III nerve palsy. Therefore the Ex should "think circuitry" by visualizing the course of the pyramidal tract to try to locate a site where it comes into anatomic relation with a somatosensory pathway and CrN III.

   3. The association of an LMN III nerve palsy on the left and hemiplegia of the right extremities suggests a lesion in the basis of the □ mesencephalon/ □ pons/□ medulla on the □ right/□ left side.

      ☑ mesencephalon; □ left (Fig. 2-16)

   4. Slight involvement of the medial lemniscus on the left could explain the sensory deficit on the right and indicate extension of the lesion from the basis into the tegmentum.

   5. Magnetic resonance imaging showed patchy lucencies in the midbrain tegmentum and an overt infarct in the midbrain basis, where CrN III runs through it medially. At the midbrain level, the pathway for somatic sensation via the medial lemniscus had crossed the midline. Review Fig. 2-18 to see how a midbrain lesion could explain the III nerve palsy, right-sided pyramidal tract signs, and right-sided sensory findings. The Pt had the classic localizing findings of a brainstem lesion: a cranial nerve palsy on one side, and long tract signs on the other (Fig. 6-19).

   6. What normal findings in this Pt would indicate that the lesion for the most part spares the dorsal part of the midbrain? (Hint: Review Figs. 2-18 and Fig. 6-19 to see what structures would have caused clinical signs if they had been destroyed. Does he show signs of the rostral midbrain syndrome (Table 5-2), or cerebellar signs in the left extremities?)

      ___________________________________________________________________

      __________________________________________________________

      Extensive, particularly bilateral midbrain tegmental lesions would cause ataxia or tremor of the left extremities, palsy of CrN III on the left, disturbances of vertical gaze, convergence nystagmus, worse sensory loss, or coma.

4. Clinical course: After several days the MSRs on the right became hyperactive, and spasticity, clonus, and a classic extensor toe sign appeared. The Pt did not regain any useful movements of his arm or fingers and could only walk when he wore a brace to support his knee. The III nerve palsy improved, but he remained with diplopia. The sensory loss disappeared, indicating only a transient ischemia of the medial lemniscus.

5. Course of corticobulbar fibers to the facial nucleus

   1. Because the Pt's hemiparesis included his face, the corticobulbar axons must have been in the basis of the midbrain. Infarcts of the basis pontis typically affect the face. The much rarer infarcts of the basis of the medulla (the medullary pyramids) often spare the face. What do these facts tell you about how far down the brainstem the fibers to the face travel?

      _______________________________________________________________

      _______________________________________________________________

      The corticobulbar fibers generally accompany the other pyramidal tract fibers to the caudal end of the pons before departing for the CrN VII nucleus in the pontine tegmentum. Medullary pyramid lesions usually spare the UMN facial fibers, because they have already left the tract (Ropper et al, 1979).

BIBLIOGRAPHY · The Pyramidal Tract

A. The theory of deficit and release phenomena

By this time, the array of positive and negative effects of neurologic lesions may seem puzzling, but we can subsume them under a theory of deficit and release phenomena.

1. Deficit phenomena are sensorimotor functions that the Pt loses after a neurologic lesion, e.g., loss of movement or loss of vision.

2. Release phenomena are sensorimotor functions that increase or first emerge after a neurologic lesion. The release phenomenon may consist of an exaggeration of a normal action, e.g., hyperactive MSRs, or a new response, e.g., the change in the behavior of the large toe from flexion to extension (Babinski sign).

B. Deficit and release phenomena after upper motoneuron (pyramidal) lesions

1. Review the components of the UMN syndrome (Table 7-7) and list the deficit and release phenomena seen in the classic or chronic stage.

   1. Deficit phenomena:

      _______________________________________________________________

      _________________________________

      Paresis or paralysis, mild disuse atrophy, and absence of abdominal and cremasteric reflexes that may return.

   2. Release phenomena:

      _______________________________________________________________

      _________________________________

      Hyperactive MSRs, clonus, spasticity, and an extensor toe sign.

2. The extensor toe sign would be classed as a □ deficit/□ release phenomenon because

   _________________________________________________________________

   _________________________________

   ☑ release

   It is a new behavior or response not present before the UMN lesion and is unmasked or released by the UMN lesion.

3. In the acute phase after pyramidal tract interruption, particularly after spinal cord transection, the Pt may show only □ deficit/□ release and no □ deficit/□ release phenomena.

   ☑ deficit; ☑ release

C. Pathophysiology of release phenomena

1. Release phenomena appear because the lesion has interrupted connections that presumably inhibited or suppressed the overactive function and because some intact pathway positively drives the overactivity.

2. Whether interruption of the pyramidal tract alone accounts for all of the release phenomena of the UMN syndrome remains unclear, but the clinician will make few errors in localization by assuming that pyramidal tract interruption is a necessary and sufficient condition for the full UMN syndrome to appear. However, involvement of other sensory and motor pathways may condition the expression and degree of the various components of the UMN syndrome.

D. Deficit and release phenomena after lower motoneuron lesions

By a stretch of the imagination, we can extend the deficit-release concept to the peripheral nervous system and even the sensory pathways.

1. Deficit phenomena after LMN lesions consist of:

   1. Paresis or paralysis of individual muscles in a segmental or peripheral nerve distribution.

   2. Decreased or absent MSRs.

   3. Denervation atrophy (early and severe atrophy).

2. Release phenomena after LMN lesions consist of:

   1. Fasciculations.

   2. Fibrillations.

3. Regarding fasciculations, the disease of the LMN "releases" the depolarization mechanism of its own neuronal membrane, allowing the motor unit to fire randomly. In the case of fibrillations, the denervation "releases" the depolarization mechanism of the individual muscle fibers, allowing them to fire randomly.

E. Deficit phenomena after interruption of autonomic motor axons

1. Paralysis and atony of smooth muscle, thus abolishing peristalsis, propulsion, and emptying.

2. Vasomotor paralysis, with vasodilation, orthostatic hypotension, and impotence.

3. Anhidrosis.

4. Trophic changes consisting of hair loss, atrophy of skin, and dystrophy of nails.

F. Autonomic release or irritative phenomena after peripheral nerve lesions

In certain instances, lesions of peripheral nerves (or spinal cord lesions) release autonomic signs consisting of hyperhidrosis or vasoconstriction, rather than anhidrosis and vasodilation (see causalgia in Chapter 10).

G. Deficit and release phenomena after lesions of the basal motor nuclei

See Section M, page 303.

A. Introduction to the concept of voluntary and involuntary movements and the notion of free will

1. We experience ourselves as having free will. This experience leads us to classify behaviors intuitively as voluntary and involuntary. But then we must puzzle over behaviors such as breathing, bladder and bowel emptying, and postural reflexes that straddle the voluntary-involuntary dichotomy. For example, you can freely will yourself to hold your breath for a period of time, but ultimately you simply have to breathe. You have no choice. The physiologic imperative to act (i.e., to emit a certain behavior) overpowers the will. Mentally ill Pts often experience their behaviors and even their very thoughts as involuntary or directed by external forces. Thus, Pts come to the physician because they experience behaviors and thoughts that they cannot willfully control.

2. By virtue of operational definitions, we can identify certain movements and behaviors that we can agree to class as voluntary or involuntary.

B. Working definition of voluntary and involuntary movements (behaviors)

1. A voluntary movement is one that the standard normal person can start or stop at the person's own command or an observer's command.

2. An involuntary movement is one that the standard normal person does not start and cannot stop at the person's own or an observer's command.

   1. As strictly construed by neurologists, involuntary movements mean those patterns of muscle contractions (tremors and other movement sequences) caused by identifiable structural or biochemical lesions in the circuitry of the basal motor nuclei, reticular formation, and cerebellum.

   2. Broadly construed, the concept of involuntary movements can also include the gamut of muscle fiber contractions of peripheral and central origins, extending from fibrillations to epileptic seizures.

3. Write out the definition of behavior given in Chapter 1, page 1:

   __________________________________________________________________

   _________________________________.

4. Reread the statements in B1 to 2 a and 2b above and substitute the word behavior for movement. It will give you a different feeling for the definition of behavior.

C. Clinical operations for identifying voluntary and involuntary movements

Neurologic lesions result in patterns of involuntary movements, recognizable from the history, inspection, and sometimes requiring laboratory tests, as for fasciculations. The operations for clinical analysis of involuntary movements follow.

1. Find out when the movements started, what conditions trigger or alleviate the movements, their relation to sleep and emotion, and their evolution over time. In other words, what is the history?

2. Describe the pattern of the movements, their distribution, rate, amplitude, and force. In other words, what are the physical findings?

3. Inspection is pivotal, allowing recognition without recourse to the Pt's testimony, in most cases. To see is to diagnose, because most involuntary movements fall into stereotyped, identifiable patterns (Fig. 15-4).

D. Some normal involuntary movements

1. Physiologic synkinesia (syn = with; kinesis motion): A synkinesis is an involuntary or automatic movement that accompanies a voluntary movement. If you voluntarily close your eyes, your eyeballs automatically roll up (Bell's phenomenon). Walk and your arms swing. Lean forward and your leg muscles automatically brace. Use these examples to identify other synkinesias (Hint: What about convergence of the eyes?). The degree of volition in the synkinesias varies. You can't stop Bell's phenomenon, but you can stop your arms from swinging when you walk.

2. Myoclonic jerks

   1. Myoclonic jerks are sudden, brief, shock-like, involuntary twitches of individual muscles or sets of muscles. A myoclonic twitch may appear in a single muscle, such as the biceps, perhaps after unaccustomed work. Or a more widespread startle response may cause an upright jerk of the head as when the person is falling asleep. A sudden discharge in the reticular activating system of the brainstem causes the lightening, myoclonic jerk of the head and the sudden restoration of consciousness. Myoclonus may occur at rest or provoked by voluntary action (action myoclonus), or triggered by diverse stimuli (stimulus-sensitive or reflex myoclonus).

   2. Epileptic myoclonic jerks, often refractory to treatment, occur in many CNS diseases. What is physiologic under one circumstance is pathologic under another.

   3. Myoclonic jerks are separate from fasciculations. Define a fasciculation.

      _______________________________________________________________

      _______________________________________________________________

      A fasciculation is a muscular twitch caused by random discharge of an LMN and its fascicle of muscle fibers (a motor unit discharge).

   4. A twitch of the entire muscle or groups of muscles is called a _____________________ jerk, whereas a twitch of a single fascicle of muscle is called a _____________________.

      myoclonus; fasciculation

3. Benign fasciculations

   1. Fasciculations appear in some normal persons, particularly after exercise. If the person has no weakness or other signs of LMN disease, the diagnosis is benign fasciculations. Twitching of an eyelid is an example.

   2. What clinical and EMG findings would differentiate pathologic from benign fasciculations?

      _______________________________________________________________

      _______________________________________________________________

      If LMN disease causes the fasciculations, the Ex should find the full syndrome of LMN disease: weakness, hypoor areflexia, hypotonia, and denervation atrophy, as supported by fibrillations and giant polyphasic motor units in the EMG.

4. Physiologic tremor: See next section.

E. Tremors

1. Definition: Tremors are rhythmic, involuntary, oscillations of one or more regions of the body (Fig. 7-38).

2. Clinical characteristics of tremors: Types of tremors differ in distribution, rate, and amplitude and whether they occur at rest or during voluntary muscular contractions. They also differ in response to drugs, in response to sleep and emotion, and in pathogenesis.

   1. Distribution: Tremors most commonly affect the head, jaw, tongue, palate, and hands but may affect the trunk or legs.

   2. Rate: Tremors vary in rate between 3 and 12 cps.

   3. Amplitude: Tremors vary from barely perceptible to gross.

   4. Relation to rest and volitional muscular contractions: Tremors dichotomize into two main groups: rest tremor and action tremors. Action tremors appear during voluntary muscular contractions, either to move a part or to maintain a voluntary posture. Action tremors include postural, kinetic, isometric, and task-specific types (Fig. 7-38).

   5. Response of tremors to drugs: Drugs may increase or decrease tremor. Tremors commonly accompany lithium treatment. Anticholinergic drugs or dopamine decrease the tremor of parkinsonism. Alcohol and propranolol decrease physiologic or essential tremor, whereas adrenalin increases them. Tremors, "the shakes," commonly follow withdrawal from alcohol and other drugs.

   6. Response of tremors to sleep and emotion: Like virtually all involuntary movements, tremors generally increase during emotional stress but dampen or disappear during tranquility and cease during sleep (Chokroverty et al., 2002).

   7. Lesion site for tremors: No single "tremorogenic" center exists. Tremors generally arise from disruption of the feedback circuits of the basal motor nuclei (Fig. 2-31), inferior olivary nucleus, and the cerebellum. Occasionally tremors occur with peripheral neuropathies.

3. Clinical characteristics of tremor types: Inspect the Pt for tremors under three conditions: rest, maintaining a posture, and during movement (Bain, 2002).

   1. Rest (or resting) tremor is a tremor when the body parts are at complete rest, supported against gravity. Have the Pt sit with the arms relaxed and the forearms supported by the thighs or recline. Look for a tremor of the fingers and hands.

      1. Rest tremor generally disappears during voluntary movement but increases during mental stress such as counting backward or when walking or moving another body part.

      2. The Ex can bring out a minimal or inapparent tremor or increase the amplitude of a rest tremor of the hands by having the Pt move the head from side to side (Froment's maneuver).

      3. Rest tremor is highly characteristic of parkinsonism.

   2. Postural or position maintenance tremor occurs during the maintenance of any intentional posture, such as holding the head up, the trunk erect, or the arms out stretched. Postural tremor qualifies as an action tremor (Fig. 7-38) because the "action" refers to the sustained volitional contraction to hold the part in position. The hands, when extended in front, show a regular, rhythmic tremor of several cycles per second. If the Pt brings the finger in to touch his nose, intention tremor may appear. As the finger approaches the nose and the Pt attempts to stop the finger to maintain a position, the tremor reappears or heightens as an end point or terminal tremor. When the finger actually touches the nose, the tremor may or may not dampen. When the Pt returns his hands to his lap, at rest, any such action tremor disappears.

   3. Kinetic tremor or intention tremor (also called ataxic tremor) may appear during any voluntary movement. At rest, the hand remains still, but upon movement, as when the Pt does the finger-to-nose test, mild to moderate deviations detour the part from a straight line path. Intention and end-point tremor appear in various degrees and combinations. They implicate a lesion of the cerebellum or its efferent pathways.

   4. Task-specific tremors appear during defined tasks, such as writing. An orthostatic tremor, a very fine, rapid, 16-cps tremor of the legs appears mainly when the Pt stands, usually combined with a general feeling of unsteadiness. Some patients experience sudden falls. Listening to the muscles with the bell of the stethoscope may demonstrate the tremor (Gershlager et al., 2004). Isometric tremor appears during a sustained muscular contraction against a stationary object.

   5. Mixed tremors: A particular type of mixed tremor that appears at rest, while maintaining a posture, and that becomes severe during voluntary movement often follows trauma to the midbrain or other midbrain lesions (Samie et al., 1990). Because the lesion affects the region of the red nucleus, this mixed type of tremor is called rubral or Holmes' tremor, implying a lesion of the dentatorubral or dentatothalamic tract, in the superior cerebellar peduncle pathway (Samie et al., 1990). Holmes' tremor mainly involves the hand and proximal arm, and is mostly unilateral. Dystonic tremor is a postural and kinetic tremor, usually not present at rest, and typically involving the body part affected by dystonia (Deuschl, 2003).

F. Kymographic records of tremors

1. From these kymographic recordings, identify the type of tremor and the pathophysiologic basis:

   1. The Pt is sitting quietly in a chair. An accelerometer attached to a hand records this tremor (Fig. 7-39).

   2. The rate of the tremor is about ____ cps.

      5 or 6

   3. Because the tremor occurs at rest but disappears during intentional movement, it qualifies as a □ rest/□ intention/□ postural tremor.

      ☑ rest

   4. This type of tremor signifies a lesion of the extrapyramidal pathways and is characteristic of the disorder called _________________ (eponym).

      parkinsonism

2. The next Pt was sitting quietly, holding her arms extended in front, at shoulder level. Only a faint instability appeared. Figure 7-40 shows the tremor when the Pt attempted to touch her index finger to her nose. After she reached her nose, the tremor increased somewhat.

   1. The tremor illustrated in Fig. 7-40 is called __________________ tremor.

      kinetic, intention, or ataxic

   2. It signifies a lesion of the □ pyramidal/□ basal ganglia/□ cerebellar pathways.

      ☑ cerebellar

3. The next Pt had no tremor when sitting still, but when she held her arms straight out, a tremor appeared (Fig. 7-41).

   1. After she reached her nose, the tremor was accentuated. The tremor shown in the initial phase (Fig. 7-41), when the Pt was holding her arms extended and still, is called □ resting/□ physiological/□ postural tremor.

      ☑ postural

   2. It signifies a lesion of the ___________________ or its efferent pathways.

      cerebellum

   3. Because it may dampen during movement, postural tremor is like □ parkinsonian/□ intention/□ essential tremor.

      ☑ parkinsonian

   4. Give the full clinical characteristics of parkinsonian tremor.

      _______________________________________________________________

      _______________________________________________________________

      Parkinsonian tremor appears at rest, has a low amplitude and a regular frequency of around 5 cps, disappears during intentional movement and sleep, and increases during emotional stress.

G. Clinical features of several common tremor syndromes

1. Physiologic tremor

   1. Self-demonstration of physiologic tremor: Insert a large sheet of paper between your index finger and the adjacent finger and hold your arm straight out in front of you. The rustling of the paper demonstrates physiologic tremor. The tremor has a frequency of about 10 cps.

   2. Physiologic tremor is generally low in amplitude, relatively rapid (6 to 13 cps), and is most evident during movement or when a part sustains a posture. It varies from 6 cps in childhood, to 8 to 13 cps in adulthood, and back to around 6 cps in senility.

   3. Physiologic tremor arises from a combination of neurally mediated oscillations and the ballistic effects of respiratory and cardiac actions (ballistocardiogram). Thus, it has neurologic and mechanical origins.

2. Emotional tremor, a normal phenomenon, to be distinguished from psychogenic tremor, is an enhanced physiologic tremor. It occurs at rest, but it worsens during volitional movement: Witness the quivering knees and quivering voice of the novice orator. From personal experience you know that emotional tremor is □ rapid/ □ very slow and of □ very great/□ relatively low amplitude.

   ☑ rapid; ☑ relatively low

3. Essential (familial) tremor

   1. This autosomal dominant or sporadic disorder resembles physiologic tremor in frequency, with a range of 4 to 12 cps, but has a greater amplitude.

   2. It affects the hands predominantly but may affect the head, bulbar muscles, and voice (Lou and Jankovic, 1989; Louis, 2001). It typically appears during a sustained posture but may appear during voluntary movements. It generally dampens or disappears with the Pt at rest. Tremors involving the tongue, trunk and lower limbs are rarely encountered.

   3. The lesion site is unknown (Rajput et al., 1991).

4. Essential palatal tremor versus symptomatic palatal tremor (palatal myoclonus)

   1. Palatal tremor has the characteristics of essential tremor. The Pt may experience an audible click. The tremor disappears during sleep.

   2. A disorder formerly called palatal myoclonus has a frequency of 110 to 160 beats/min. It may affect other bulbar muscles derived from the branchial arches. It violates the law of disappearance of involuntary movements during sleep because it persists. It follows, with variable delays, lesions in the triangle between the cerebellum red nucleus, central tegmental tract, and inferior olivary nucleus (Mollaret's triangle).

5. Senile tremor has a frequency of about 6 to 10 cps. Senile and familial tremors merge in their clinical manifestations, but senile tremor, although frequently familial, may result from nonfamilial lesions of aging.

6. Parkinsonian tremor (Jankovic and Tolosa, 1998)

   1. Parkinsonian tremor has a frequency of 3 to 6 cps and low to moderate amplitude. Drum your fingertips on the table, timing 25 beats per 5 seconds, to observe two features of this tremor: moderate frequency and relatively low amplitude. It appears when the part is at rest, increases during mental and emotional tension, but disappears or dampens during intentional movement, and is absent during sleep. Often it appears asymmetrically. Typically affecting the hands and digits, the rustling of the thumb against the pads of the fingers resembles pill-rolling; hence its name, pill-rolling tremor. Voluntary head movements enhance the tremor (Froment's maneuver).

   2. A 4- to 8-cps postural tremor occurs also about as often as the classic rest tremor (Brooks, 2002).

   3. Degeneration of the dopaminergic pathway that runs from the substantia nigra of the midbrain to the striatum causes parkinsonism, but other neurons also degenerate. The parkinsonian triad of rest tremor, lead-pipe rigidity, and hypokinesia may appear as an entity or with associated widespread neuronal degeneration, known as the Parkinson plus syndromes (Victor and Ropper, 2001).

   4. Parkinsonian tremor differs from most tremors by □ increasing/□ decreasing during volitional movement, and resembles other involuntary movements by □ increasing/□ decreasing during emotional stress and □ increasing/□ disappearing during sleep.

      ☑ decreasing; ☑ increasing; ☑ disappearing

   5. The rest tremor of parkinsonism, a hyperkinesia, contrasts with a reduction in the overall mobility of the Pt, called bradykinesia or hypokinesia. Paradoxically, an irresistible need to move, a physiologic imperative called akathisia (see Section XII P) also plagues the Pt, requiring abrupt, restless shifts of position against the background of bradykinesis and muscular rigidity. In a given Pt, one or more of the signs may predominate. Thus, one Pt displays mainly tremor and the next mainly rigidity. The basic motor signs of parkinsonism include a quatrain of:

      1. Rest tremor

      2. Lead-pipe rigidity, often with a "cogwheeling," ratchet-like yielding due to the superimposition of the beats of the tremor

      3. Overall bradykinesia

      4. Postural instability

   6. Derivative signs of the rigidity of the laryngeal muscles are loss of inflections of the voice, resulting in a characteristic monotonous tone, i.e., plateau speech, and words running together (Caekebeke et al., 1991). Rigidity of the facial muscles results in an absence of emotional expression, i.e., a masked face.

   7. Oculogyric crises are spasms of upward deviation of the eyes or of the eyes and head. Common in post-encephalitic parkinsonism, oculogyric crises may occur in other disorders of the basal motor nuclei. Summarize for yourself the motor manifestations of parkinsonism.

   8. Neurologic evaluation scales for following the course of parkinsonism document changes in their status (Gollomp, 2002; www.wemove.org).

7. Neuropathic tremor: This tremor, usually an action type, occurs with a variety of acquired or hereditary peripheral neuropathies, more commonly with demyelinating than with axonal types (Bain, 2002). The tremors are mainly postural and action tremors.

8. Drug-induced and toxic tremors: A number of tremors, as with hyperthyroidism, lithium treatment, delirium, and drug over dosage or withdrawal (including alcohol), share features of one or more of the foregoing types of tremors or come from an enhancement of physiologic tremor.

9. Psychogenic tremors have inconsistent, complicated patterns that change with circumstances (Koller et al., 1989). Most of these tremors are action tremors. They often develop suddenly and sometimes have spontaneous remissions. The tremor decreases during distraction or volitional movement of the contralateral hand. When the Ex tests for muscle tone, the Pt shows resistance to passive movement of the joint, indicating increased tone of the part, and the tremor stops briefly, which is known as the coactivation sign (Deuschl et al., 1998). See Chapter 14 for other clinical features of psychogenic disorders.

H. Disorders to differentiate from tremors

1. Clonus is a repetitive MSR.

2. Asterixis consists of sudden lapses of a sustained posture, which may have a periodic or pseudo-rhythmic frequency. To elicit asterixis, ask the Pt to extend the arms straight out, with the wrists dorsiflexed. The wrist will then periodically drop and immediately re-extend. First described in hepatic encephalopathy, it also appears in other metabolic-toxic encephalopathies and after structural lesions of the cerebello-thalamo-cortical circuits (Victor and Ropper, 2001; Kim, 2002).

3. Myoclonus

   1. Myoclonus means shock-like, lightning fast contractions of parts of muscles or groups of muscles. Individual movements are very brief but may be repetitive. They are irregular in rate and amplitude and symmetric or asymmetric (Victor and Ropper, 2001).

   2. When restricted to one group of muscles, it is called segmental myoclonus clonus or myoclonus simplex.

   3. When widespread, the movements are myoclonus multiplex or polymyoclonus.

   4. Myoclonus appears in a large number of metabolic, toxic, and degenerative diseases and types of epilepsy and may arise from lesions at the spinal level. Many different disorders that do not belong together are semantically linked by the term myoclonus.

   5. The distinction between polymyoclonus, chorea, severe ataxia, hyperexplexia, and multiple tics is sometimes difficult.

   6. A distinctive syndrome of opsoclonus and polymyoclonus affects children as an autoimmune disorder and as a distant effect of neuroblastoma. Personality changes are usual, particularly irritability.

4. Rhythmic myoclonus versus so-called cortical tremor: The Pt shows intermittent brief jerks, irregular or rhythmic, of slow frequency and often limited to segmental levels (Deuschl et al., 1998). Cortical tremor consists of high-frequency jerks (7 to 18 cps) similar to high-frequency postural tremor. Epileptiform discharges appear in the electroencephalogram (EEG).

5. Partial continual epilepsy (of Kozhevnikoff/Kojewnikow): The Pt shows continuous low-frequency jerks of one muscle group days and nights for weeks, months to years. The EEG shows focal epileptiform discharges.

I. Review of tremors

Before proceeding with the text, review the tremor hyperkinesias by actually acting them out (Figs. 7-38 to 7-41). If you feel the need to, organize your own table or make a personal differential diagnostic dendrogram.

BIBLIOGRAPHY · Tremor and Parkinsonism

J. Non-tremor types of hyperkinesias

1. Several hyperkinesia display characteristic clinical features that predict the lesion site (Table 7-8). (Chokroverty, 1990; Klawans et al., 1988; Lang and Weiner, 1992).

2. Chorea refers to incessant, random, moderately quick movements—a grimace, elevation of a finger or arm, a misstep when walking, an interruption when speaking. Overall, chorea resembles the "fidgets." One part or another of the body is flickering into motion all of the time. The movements resemble a choreographer working out the movements for a dance or, perhaps better described, they simulate fragments of normal movements. For instance, at one time or another, after you start to make an inappropriate movement (perhaps reaching up to pick your nose), you may suddenly decide to arrest it midway. Or after starting such a movement, you may have diverted it to brushing back your hair. Patients with chorea may employ this ruse. Nevertheless, an observer can perceive the stoppage or the diversion in the continuity of the initial movement.

3. Athetosis refers to slow, writhing movements of the fingers and extremities. If severe, athetosis affects speech and some proximal movements. These movements wax and wane and generally do not hold the part in a fixed posture. Athetosis often accompanies or follows partial interruption of the pyramidal tracts, particularly in Pts with cerebral palsy and spastic quadriplegia or diplegia. The quick random fidgety movements, called ________________, contrast with the slow writhing distal movements, called __________________.

   chorea; athetosis

4. Dystonia refers to prolonged, slow, alternating contraction and relaxation of agonists and antagonists. The prolonged muscular contractions hold the part in one position for periods and may lead to pretzel-like body positions with fixed scoliosis and fixed contractures of joints.

   1. Focal dystonia, such as spasmodic torticollis and writer's cramp, may affect more or less restricted groups of muscles.

   2. The sustained postural deviations of dystonia differ from the quick movements of chorea and the slower writhing, mainly distal movements called ____________________.

      athetosis

   3. Although dystonia is traditionally classed as an extrapyramidal movement disorder, the lesion site and pathophysiology of the hereditary form are unknown (Zeman and Dyken, 1968), but dystonia can result from known, acquired lesions of the basal motor nuclei (Zeman and Whitlock, 1968).

5. Hemiballismus refers to violent flinging movements of one-half of the body. Ballista means to throw, as in ballistics. The Pt's arm thrashes about as if it were trying to fling away a handful of snakes. Hemiballismus usually appears abruptly in elderly hypertensive Pts. The lesion is predictable. A peculiar, sharply delimited hemorrhage destroys the contralateral subthalamic nucleus of Luys or its immediate surrounding pathways. This almond-sized and almond-shaped diencephalic nucleus belongs to the basal motor nuclei. Hemiballismus may also result from lesions in the caudate, putamen, globus pallidus, precentral gyrus, or thalamic nuclei.

6. Tics are quick, lightning fast, stereotyped, involuntary movements of face, tongue, upper extremities, or phonations. (Jankovic and Tolosa, 1998). In contrast to the preceding hyperkinesias, the sequence of movements is identical each time if the Pt has one type of tic. However, the Pt may have multiple kinds of tics. All of us display minor tics: wrinkling of the forehead, followed by blinking the eyes, or hitching up the trousers, or a shrug of the shoulder. Athletes display a number of tic-like maneuvers, as when a basketball player prepares to shoot a free throw, or a tennis player prepares to serve. Tics increase during emotional stress, are less prominent during periods of concentration, and often abate during sleep. Although mostly of low amplitude, tics, when violent, may throw the Pt to the floor, thus resembling an exaggerated startle response called hyperexplexia. Of the movement disorders discussed, tics, being quick and usually of low to moderate amplitude, most closely resemble □ chorea/□ athetosis/□ hemiballismus.

   ☑ chorea

7. Multiple tic syndrome of Gilles de la Tourette: Some tics are regarded as psychogenic, but they figure prominently in an organic disorder called Tourette's syndrome, which has three major features:

   1. Multiple tics that change from time to time.

   2. Involuntary respiratory actions and vocalizations with squawks, barks, howls or sniffs, humming, and sometimes the involuntary utterance of expletives.

   3. Personality traits: sometimes rigid, obsessive-compulsive, or abrasive (Kurlan, et al., 2002; Leckman and Cohen, 1999) and attention deficit hyperactivity disorder (Tourette's Syndrome Study Group, 2002).

K. Continuum between the named types of hyperkinesias

Dystonia, athetosis, chorea, and tics represent way stations along a continuum of involuntary movements, not necessarily discrete entities. They differ perhaps more in their speed than in any other way. Tics and chorea are the fastest, with each movement measured in a second or even less. Next comes athetosis, lasting just a little longer, in seconds. Then comes dystonia, which lasts many seconds to minutes or even longer, as in spasmodic torticollis, a form of dystonia in which the head remains deviated for long periods.

As an oversimplified, 1, 2, 3 mnemonic, think of each tic as shorter than 1 second (but the same tic may be repetitive), individual choreiform movements as lasting 1 second, athetosis as lasting 1 to 3 seconds (but the movements may flow into one another), and dystonia as lasting from 3 seconds to minutes or longer.

Hemiballismus differs from chorea in its more violent amplitude and unilaterality. Hemichorea may occur, but it is most frequently bilateral, as in Huntington's or Sydenham's chorea.

L. Drug-induced extrapyramidal movement syndromes and the tardive dyskinesias

Various tranquilizers, antipsychotics, and antidepressant drugs alter the balance of neurotransmitters in the basal motor circuits (Yassa et al., 1990). These chemical lesions mimic the effect of anatomic lesions in producing hypo- and hyperkinesias, ranging from parkinsonism to dystonia. The involuntary movements often predominately affect facial, oral, buccal, and pharyngeal movements, with dysphonia and dysphagia (Meige's syndrome; Lang and Weiner, 1992). Unfortunately, tardive dyskinesia may be permanent and very resistant to therapy. Levodopa, used to treat parkinsonism, also produces dyskinesias (Olanow, 2000).

M. The concept of deficit and release phenomena after lesions of the basal motor connections

For general discussion, see Section XI of this chapter.

1. Deficit phenomena after lesions of the basal motor circuitry include overall bradykinesia, gait impairment, masked facies, and loss of voice inflection.

2. Release phenomena include the hypertonia called lead-pipe rigidity, tremor (generally tremor of the part at rest), akathisia, and the patterned hyperkinesias such as tics, chorea, athetosis, dystonia, and hemiballismus. Whether the concept of release phenomena applies to these phenomena requires some stretch of the imagination. Even less does the concept apply to the other syndromes of excessive behavior, such as hyperactivity.

N. Rating scales for involuntary movement disorders

Various rating scales such as the Abnormal Involuntary Movement Scale enable the Ex to quantify various involuntary movements to determine the degree of disability, to follow the course of the disease, and to document the effects of treatment (Gollomp, 2002; Herndon, 1997; Marsden and Fahn, 1984, 1987, 1994).

O. Some simple, general tests for motor dysfunction: writing, finger-tapping speed, the Archimedes spiral, and activities of daily living

These tests are useful in analyzing most motor disorders, especially in Pts with hemiparesis, tremor, rigidity, or ataxia, not only for differential diagnosis but also to appreciate functional disability.

1. Writing: Watch the Pt write spontaneously and, if a motor disorder or cerebral disorder is suspected, write a sentence to dictation. Like the gait, most motor disorders affect writing. The ataxic dysgraphia of cerebellar disease, the micrographia of rigidity, and the tremulous dysgraphia of essential tremor stand out vividly from each other.

2. Finger-tapping speed

   1. Technique: For a convenient bedside test in lieu of an actual counter, place an ordinary audiocassette on the table and have the Pt grasp it between the thumb and third digit, leaving the index finger free to tap (Fig. 7-42). Ask the Pt to tap as rapidly as possible for several seconds. The Ex should demonstrate the test first. Normal subjects tap at rate of around 50 taps per 10 seconds. Children and the aged tap at slower rates.

   2. The cassette serves three purposes:

      1. The Ex will quickly learn about the Pt's fine motor skills.

      2. The dyspraxic Pt has difficulty assuming the position or even in picking up and arranging the box.

      3. Most important, the cassette amplifies the sound so that the Ex can estimate the speed and the rhythm. The ear can detect subtle differences between the right and left hands far better than the eye.

   3. Because the test engages the entire central and peripheral motor systems, spasticity, rigidity, ataxia, and neuromuscular disorders will slow finger-tapping speed discernibly, and the Ex will easily hear the disturbance in rhythm of the cerebellar Pt.

3. Archimedes spiral

   1. Technique: The Pt places a pen in the middle of a sheet of paper and makes a spiral line encircling the center point, making several winds of the pen, out to the periphery.

   2. The difference in rigidity that narrows the spiral but leaves its lines fairly regular, ataxia in which the spiral's lines irregularly weave in and out, and the continuous wavering of lines of essential tremor are striking.

4. Tasks of daily living: Frequently the Ex should elect to watch the Pt button, use scissors, tie shoelaces, drink a glass of water, and arrange clothes as if to put them on.

BIBLIOGRAPHY · Finger Tapping

P. Akathisia, restless legs, and hyperactivity: the urge to move

1. Akathisia refers to motor unrest manifested by continual shifting of positions and sometimes by restlessly moving about. When questioned, Pts often report an actual feeling in their muscles of an urge to move (Sachdev, 1995). Akathisia appears typically in Parkinson's disease, in other diseases of the basal motor nuclei, and with psychotropic medications.

2. Restless-legs syndrome (Ekbom's syndrome; Chokroverty and Jankovic, 1999; Ekbom, 1960): When attempting to rest or sleep, these Pts feel an irresistible urge, a necessity, to move their legs around. No force of will can hold the legs still against the pathophysiologic imperative, and the aimless, incessant wandering of the legs prevents the onset of sleep. Symptoms are partially or totally relieved by movements such as walking or stretching (Allen et al., 2003). Exhaustive exercise or some drugs, such as antihistamines, may induce restless legs.

3. The hyperactive child: Hyperactive children display incessant, rapidly changing motor activity, often starting in infancy. Their driven, inappropriate, and usually annoying activity consists of fidgeting, pushing, pulling, banging, rummaging, clamoring, whining, and running. The hyperactivity continues with little regard for other people, danger, and reward and punishment. Rather than a standard, stereotyped pattern like athetosis or dystonia, the disorder consists of the sheer quantity of activity. Usually these children are so clamorous that my secretary can already diagnose them by the noise they make as they clatter down the long hall to my office. By stretching the imagination, we might think of restless legs as a localized type of akathisia and of childhood hyperactivity as its generalized childhood counterpart. No specific known brain lesion underlies hyperactivity, but many hyperkinetic children have other subtle or overt evidence of brain damage or frank mental retardation. The foregoing syndromes of driven behavior border on a variety of cursive states such as compulsive walking or running and cursive epilepsy. All have in common an irresistible drive, a pathophysiologic imperative, to move.

4. Self-mutilation: The Pt compulsively inflicts self-injury by biting, scratching, or pounding despite punishments or rewards. The head-banging infant or child particularly distresses parents. Although generally seen in mentally retarded Pts, some individuals with normal intelligence scratch, bite fingernails, pick their nose or lips, or otherwise injure themselves compulsively (neurodermatitis) in response to some pathophysiologic imperative that overcomes willpower. Smoking with its intermittent irritation of the lungs may fall into the same category. The Pt scratches, as it were, the respiratory mucosa, but of course chemical addiction belongs to the scenario.

5. Stereotyped behavioral mannerisms: Many retarded, autistic, and some otherwise normal children and psychotic adults display repetitive behaviors, including spinning, rocking, patting, touching, grimacing, licking, and mouthing. Repetitive back arching and thigh squeezing may act as masturbatory equivalents. Children with Rett's syndrome display a characteristic hand wringing. Where these behaviors, in addition to so many of the behaviors discussed above, fall in the scale between voluntary and involuntary further stretches the notion of free will.

Q. Epilepsy

1. Definition: Epilepsy is any change in the mental, motor, or sensory state of the Pt caused by an abnormal hypersynchronous discharge of neurons.

2. Involuntary epileptic motor activity may consist of tonic or clonic spasms and myoclonic jerks that affect all or part of the body or of complex automatisms with laughter and cursive states during complex partial (psychomotor) seizures.

3. If epilepsy causes the abnormal motor activity, the Pt usually will lose consciousness and have amnesia for the episode, and EEG monitoring usually will record epileptiform activity. However, during some epileptiform movements, the Pt retains consciousness (see Chapter 13).

R. Avoiding pitfalls (pratfalls) in distinguishing psychogenic from organic motility disturbances

1. Hysterical movement disorders or malingering may imitate organic movement disorders. See Chapter 14.

2. Anxiety or emotional tension makes virtually all hyperkinesias worse, but most dampen or disappear when the Pt is relaxed or asleep. Only a few abnormal involuntary movements occur during sleep: sleep myoclonus, palatal myoclonus (actually palatal tremor), somnambulism, and some epileptic seizures.

3. During the evolution of one illness, the form of the hyperkinesias or the degree of hypo- or hypertonia may change. Hence, what starts as a flaccid hemiparesis may end as spastic hemiparesis. Simple athetosis may end as dystonia or so-called tension athetosis, in which the Pt's efforts to make a voluntary movement is paralleled by the degree of an athetoid or dystonic spasm. Torsion dystonia and tension athetosis are classic examples of pathophysiologic imperatives that determine the contraction of the muscles, rather than the Pt's "will."

4. Psychotropic medications, alcohol, and street drugs frequently cause hypokinetic or hyperkinetic movement disorders. Consider drugs in the differential diagnosis of tremors or any other movement disorder of new onset.

5. Mothers of hyperactive children invariably appear distraught, depressed, and defeated by their inability to cope with their children. Usually the child's hyperactivity discloses itself by the slapdash, frenetic way the child executes the Ex's requests. If, however, the child appears calm during the period of examination, as a few will, the Ex may mistakenly conclude that the mother is "overanxious." The usual problem is an underanxious physician, not an overanxious mother. Thus the immediate inspection of the Pt, which serves so well to recognize the standard hyperkinesias of extrapyramidal origin, may, on some occasions, fail in recognizing the hyperactive child if the observation period is too brief. On the next visit, detain the child in the waiting room for a considerable period before the appointment. Then, after the child has defaced your office décor, scattered the toys all over the reception room (without actually playing with any), exasperated your other Pts, and driven your receptionist mad, you will understand the mother's plight.

S. Patient analysis

The Pt is a mentally normal 47-year-old woman who was born with mild spastic cerebral palsy. Her motor disorder has not changed in the decades since childhood. For the serial photographs, she was requested to extend her arms out in front of her and to hold them as still as possible. Similar movements appear when she is at rest or walking. The individual movements last 2 to 3 seconds and have low to moderate force and amplitude, but may merge with each other in a continuous pattern. The movements shown in Fig. 7-43 would best be classified as __________________.

athetosis

T. A summary of involuntary movements (hyperkinesias) by operational definition

1. For clinical diagnosis, I have defined hyperkinesias broadly to include any extra muscular activity of peripheral or central origin caused by a lesion of the nervous system.

2. For the clinical characteristics in frames a to v, write down the proper descriptive diagnosis in the blank. Where possible, act out the motility disorder described.

   1. Spontaneous random contractions of denervated muscle fibers detected by EMG: ________________________.

      fibrillations

   2. Spontaneous random twitches of small parts of muscles detected by clinical inspection and EMG: ________________________.

      fasciculations

   3. Sudden spontaneous contraction of a muscle or group of muscles, which may simulate a startle reaction: ________________________.

      myoclonic jerks

   4. Spontaneous stereotyped sequence of muscular contractions, most prominent in facial muscles, in patients with obsessive-compulsive personality traits: ________________________.

      tics

   5. Spontaneous tonic or clonic jerking of the body, often accompanied by loss of consciousness: ________________________.

      epilepsy

   6. Spontaneous, quick movements simulating fragments of normal movements, usually most prominent in extremities: ________________________.

      chorea

   7. Spontaneous, writhing movements of fingers and extremities that may affect facial and axial muscles: ________________________.

      athetosis

   8. Spontaneous, long-sustained deviations of appendicular and axial parts, with alternating agonist-antagonist contractions, that may ultimately lead to fixed deformities: ________________________.

      dystonia

   9. More or less incessant (during waking hours), wild, flinging movements of one-half of the body, seen usually in elderly hypertensive patients: ________________________.

      hemiballismus

   10. Spontaneous upward deviation of the eyes and head, seen usually with rest tremor and lead-pipe rigidity: ________________________.

       oculogyric crisis

   11. Irresistible wandering of the legs, especially when the patient tries to rest or to sleep: ________________________.

       restless-legs syndrome of Ekbom

   12. Incessant, driven, usually annoying or aggressive behavior in a child: ________________________.

       hyperkinesia

   13. A tremor at rest of 6 cps, which dampens or disappears on intentional movement: ________________________.

       parkinsonian (rest) tremor

   14. Irregular tremor of a movement in progress, but no tremor at rest: ________________________.

       intention (ataxic) tremor

   15. Rapid tremor of an outstretched hand that dampens when a movement is in progress and reappears when a new posture is held: ________________________.

       postural tremor

   16. A 10-cps tremor of the hands that often has an autosomal dominant hereditary pattern: ________________________.

       familial (essential) tremor

   17. An 8-cps tremor of the head or of the head and hands occurring in an elderly patient: ________________________.

       senile tremor

   18. A therapy-resistant hyperkinesia usually with predominant face, lip, and tongue movements that appear after prolonged ingestion of psychotropic medications: ________________________.

       tardive dyskinesia

   19. A state of motor unrest in a parkinsonian Pt characterized by irresistible restless shifting of postures: ________________________.

       akathisia

   20. Sudden yielding of a sustained posture, as of the dorsiflexed wrist with the arms extended: ________________________.

       asterixis

   21. Prolonged rippling or undulating, worm-like contractions of muscles, distributed focally or in widespread groups, associated with repetitive discharges of groups of motor units: ________________________.

       myokymia

   22. Irregular, quick, low amplitude, widespread movements of trunk and extremities, often associated with opsoclonus: ________________________.

       polymyoclonus

BIBLIOGRAPHY · Involuntary Movements

Demonstrate the motor examination, commencing with the initial inspection for gait, posture, tremors, and abnormal movements; followed by palpation, strength testing, and muscle tone; and proceeding through the deep reflexes, percussion, and superficial reflexes.