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Disease is of antiquity and nothing about it changes. It is we who change as we learn to recognize what was formerly imperceptible.

—Jean Martin Charcot (1825–1893)


A. Symptoms and signs of neurologic disease

Diseases that affect the nervous system manifest by mental, motor, or sensory symptoms and signs and by abnormal body contours (Fig. 1-1).


Dendrogram summarizing neurologic symptoms and signs.

B. Steps in the neurologic examination

  1. The neurologic examination (NE) consists of a series of simple, standardized steps. Each step focuses on a specific, readable end point. Most steps test a known neuroanatomic circuit. As end points, the examiner (Ex) selects:

    1. Simple behaviors, such as a pupil constricting to light or a finger flexing.

    2. Complex behaviors, such as walking, speaking, or writing.

    3. Specific body contours, such as head size or shape.

  2. The Ex compares the result of each step with a "standard person" of like age, sex, and culture and judges each result as normal, borderline, or abnormal.

  3. The steps use four types of operations: inspections, questions, requests, and maneuvers.

    1. Inspections disclose the patient's (Pt's) bodily contours and spontaneous and elicited behaviors.

    2. Questions determine the Pt's mental status and sensory perceptions.

    3. Requests or commands test the Pt's volitional responses.

    4. Maneuvers impose stimuli to elicit sensations and reflexes.

C. The NE as standardized assessment of designated behaviors

  1. For the NE, we may define behavior as any detectable change produced by neural activation of an effector. The neural activation may arise voluntarily or reflexly.

  2. Because only two types of effectors exist, namely glands and muscles, humans can produce behaviors by only two actions: by secreting something and by adjusting the length of their muscle fibers.

    1. By secreting we produce sweat, tears, saliva, mucus, hormones and digestive juices, and semen.

    2. By adjusting the length of muscle fibers we can:

      1. Operate our skeletal levers to move ourselves and objects around.

      2. Open and close or vibrate our apertures: vocal cords, eyelids, mouth, and other sphincters.

      3. Move gases and liquids through our tubes (air, blood, secretions, food, feces, gametes, and urine).

  3. All human behavior consists of secreting substances or changing the length of muscles' fibers. Whatever the behavior, it originates from nerve impulses traveling through neural circuits.

  4. The definition of behavior excludes thinking per se, because the Ex cannot directly observe it. René Descartes (1596–1650) may have said, "I think therefore I am," but the Ex can gain access to the Pt's thoughts only if the Pt can display adaptive behavior, such as speaking, writing, or gesturing.

D. Corollaries of the definition of behavior

  1. All behaviors and all thoughts depend on neuroanatomic circuits.


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