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Harrison’s Manual of Medicine




Peripheral neuropathy (PN) refers to a peripheral nerve disorder of any cause. Nerve involvement may be single (mononeuropathy) or multiple (polyneuropathy); pathology may be axonal or demyelinating. An approach to pts with suspected neuropathy appears in Fig. 195-1.

FIGURE 195-1. Approach to the evaluation of peripheral neuropathies, CIDP, chronic inflammatory demyelinating polyradiculoneuropathy; EDX, electrodiagnostic studies; GBS, Guillain- Barré syndrome; IVIg, intravenous immunoglobulin. (After AK Asbury, in Harrison’s Textbook of Internal Medicine, Update IV, New York, McGraw-Hill, 1983.)

CLINICAL FEATURES   The typical axonal polyneuropathy begins with sensory symptoms (tingling or burning) distally in the toes or feet. Symptoms spread proximally to the ankles, then involve the calves. Ankle reflexes are lost. Once sensory loss reaches the knees, proximal spread extends into the thighs and numbness of fingers appears. This pattern results in a “stocking-glove” distribution of sensory and motor findings. Further progression results in loss of knee reflexes. Light touch may be perceived as uncomfortable (allodynia) or pinprick as excessively painful (hyperpathia). Weakness and atrophy evolve from distal to proximal—initial toe dorsiflexion weakness may progress to bilateral foot drop, intrinsic hand muscle weakness, or (in extreme cases) impairment of muscles needed for ventilation and sphincter function. A family history for neuropathy should be sought, since adult-onset hereditary motor and sensory neuropathy (HMSN II) is not uncommon. In contrast to axonal neuropathy, demyelinating neuropathy does not produce stocking-glove deficits; diffuse loss of reflexes and strength is usual, and nerves are often palpably enlarged.
DIAGNOSTIC EVALUATION   Diagnosis is aided by classification into axonal or demyelinating pathology (Table 195-1) and consideration of the time course of the neuropathy (Table 195-2). EMG is particularly helpful when history and examination do not clarify the diagnosis. EMG can distinguish axonal from demyelinating neuropathy, neuropathy from myopathy, nerve root or plexus disorders from distal nerve involvement, generalized polyneuropathy from mononeuropathy multiplex, and central weakness from peripheral nerve weakness. Sural nerve biopsy is helpful when vasculitis, multifocal demyelination, amyloidosis, leprosy, or sarcoidosis are considerations; biopsy results in lateral foot sensory loss, and rarely a painful neuroma may form at the biopsy site. Screening laboratory studies in a distal, symmetric axonal polyneuropathy are Hb A1C, ESR, serum protein/immunoelectrophoresis, and vitamin B12, BUN, and creatinine levels. Other studies are suggested by the differential diagnosis; it is important to recall that many systemic diseases, drugs, and toxins can produce neuropathy.

Table 195-1 Polyneuropathies (PN)a

Table 195-2 Diagnostic Considerations in Polyneuropathy


Acute inflammatory demyelinating polyneuropathy (AIDP) or Guillain- Barré syndrome (GBS): an ascending, usually demyelinating, motor > sensory polyneuropathy accompanied by areflexia, motor paralysis, and elevated CSF total protein without pleocytosis. Over two-thirds are preceded by infection with EBV or other herpesviruses, Campylobacter jejuni gastroenteritis, HIV, other viruses, or Mycoplasma. Maximum weakness is usually reached within 2 weeks; demyelination by EMG. Most pts are hospitalized; one-third require ventilatory assistance. 85% make a complete or near-complete recovery with supportive care. Intravenous immune globulin (IVIg) (2 g/kg given over 5 d) or plasmapheresis (40–50 mL/kg daily for 4–5 d) significantly shorten the course. Glucocorticoids are ineffective. Variants of GBS include Fisher syndrome (ophthalmoparesis, facial diplegia, ataxia, areflexia; associated with antibodies to ganglioside GQ1b) and acute motor axonal neuropathy (more severe course than demyelinating GBS; antibodies to GM1 in some cases).

Chronic inflammatory demyelinating polyneuropathy (CIDP): a slowly progressive or relapsing polyneuropathy characterized by diffuse hyporeflexia or areflexia, diffuse weakness, elevated CSF protein without pleocytosis, and demyelination by EMG. Begin treatment when progression is rapid or walking is compromised. Initial treatment is usually IVIg; most pts require periodic retreatment at 6-week intervals. Other treatment options include plasmapheresis or glucocorticoids; immunosuppressants (azothiaprine, methotrexate, cyclophosphamide) used in refractory cases.

Diabetic neuropathy: typically a distal symmetric, sensorimotor, axonal polyneuropathy, but many variations occur. A mixture of demyelination and axonal loss is frequent. Isolated sixth or third cranial nerve palsies, asymmetric proximal motor neuropathy in the legs, truncal neuropathy, autonomic neuropathy, and an increased frequency of entrapment neuropathy at common sites of nerve compression all occur.

Mononeuropathy multiplex (MM): defined as involvement of multiple noncontiguous nerves. One-third of adults with MM have an acquired demyelinating disorder that is treatable. The remainder have an axonal disorder; 50% of these have vasculitis—usually due to a connective tissue disorder. In this latter group, immunosuppressive treatment of the underlying disease is indicated.
CLINICAL FEATURES   Mononeuropathies are usually caused by trauma, compression, or entrapment. Sensory and motor symptoms are in the distribution of a single nerve—most commonly ulnar or median nerves in the arms or peroneal nerve in the leg. Clinical features favoring conservative management of median neuropathy at the wrist (carpal tunnel syndrome) or ulnar neuropathy at the elbow include sudden onset, no motor deficit, few or no sensory findings (pain or paresthesia may be present), and no evidence of axonal loss by EMG. Factors favoring surgical decompression include chronic course (lack of response to conservative treatment), motor deficit, and electrodiagnostic evidence of axonal loss. Patterns of weakness, sensory loss, and conservative/ surgical treatment options are listed in Table 195-3.

Table 195-3 Common Mononeuropathies—Findings and Treatment


For a more detailed discussion, see Asbury AK: Approach to the Patient With Peripheral Neuropathy, Chap. 377, p. 2498; and Asbury AK, Hauser SL: Guillain-Barré Syndrome and Other Immune-Mediated Neuropathies, Chap. 378, p. 2507, in HPIM-15.


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