Neuropathy is defined as a disease or injury of the peripheral sensory, motor, or autonomic nerves. It is usually categorized separately from selective injury to the cell body of the axon (neuronopathy), injury to the nerve roots distal to their origin (radiculopathy), or injury to the brachial or lumbosacral plexus (plexopathy). Neuropathy may be pure motor, pure sensory, or mixed sensorimotor. It may occur symmetrically throughout the body (polyneuropathy), individually in single nerves (mononeuropathy), or in multiple, individual nerves (multifocal neuropathy or mononeuritis multiplex). Autonomic neuropathy may be part of a generalized neuropathy or occur independently. Disorders of the autonomic nervous system are discussed in Chapter 21.
Mononeuropathies, particularly those resulting from nerve entrapment, are among the most common diseases affecting the general population. Individuals employed in occupations with actions requiring high force and repetitive motion, such as food processing, carpentry, and roofing are at increased risk. Median nerve entrapment resulting from carpal tunnel syndrome is the most common mononeuropathy, with a symptomatic prevalence of 14% and a much higher lifetime incidence. The ulnar and fibular (formerly peroneal) nerves are also commonly injured (at the elbow and the knee, respectively).
Mononeuropathy can also result from multifocal demyelination (eg, Lewis Sumner variant of chronic inflammatory demyelinating polyneuropathy [CIDP]), from ischemic injury as a result of impairment of the vascular supply to an individual nerve (eg, mononeuropathy multiplex), or from trauma (Table 19–1).
Table 19–1.Common compressive mononeuropathies. ||Download (.pdf) Table 19–1. Common compressive mononeuropathies.
|Nerve ||Site(s) of Entrapment ||Cause of Compression |
|Median || |
Carpal tunnel syndrome (common)
Anterior interosseous syndrome (rare)
|Ulnar || |
Tardy ulnar palsy (common)
Cubital tunnel syndrome (rare)
Guyon canal stenosis (rare)
|Radial || |
Pressure of hard object (eg, back of chair) against inner upper arm
Entrapment of posterior interosseous nerve upon forceful supination
Superficial radial nerve (handcuff palsy)
|Lateral femoral cutaneous (lumbosacral plexus) ||Anterior superior iliac spine ||Meralgia paresthetica; compression occurs with obesity, pregnancy, tight belts |
|Femoral ||Anterior upper leg ||Compression of femoral artery postcatheterization |
|Sciatic ||Pelvis ||Piriformis syndrome; entrapment under ischial tuberosity while sitting |
|Fibular || |
At fibular head
Prolonged squatting (strawberry picker palsy)
Sitting with crossed legs (captain chair palsy)
|Tibial || |
Tarsal tunnel syndrome (rare)
Polyneuropathy has hundreds of potential etiologies, the most common of which are summarized in Table 19–2. Diabetes mellitus is the most common cause of polyneuropathy in the United States, and throughout the world, affecting at least 1–2% of the population. Leprosy remains a common cause of neuropathy worldwide. The total prevalence of chronic symmetric polyneuropathy is estimated to be approximately 3.5% in the outpatient elderly population.