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Diseases of the peripheral nerves 

Diseases of the peripheral nerves

Chapter:
Diseases of the peripheral nerves
Author(s):

R.D.M. Hadden

, P.K. Thomas

, and R.A.C. Hughes

DOI:
10.1093/med/9780199204854.003.2416_update_002

July 30, 2015: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

Update:

Chapter reviewed, minor updates made.

Small fibre neuropathy section updated.

A relevant case history from Neurological Case Histories: Case Histories in Acute Neurology and the Neurology of General Medicine has been added to this chapter.

Updated on 28 Nov 2012. The previous version of this content can be found here.
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date: 30 March 2017

Disorders of peripheral nerve function can be categorized in terms of the site of the primary disturbance. (1) Neuronopathies—conditions that lead to death of the neuron cell body and axon. (2) Axonal neuropathies—conditions that affect axons which may be focal, as in local injury, multifocal, as in vasculitis, or diffuse as in metabolic or toxic disorders often cause selective degeneration of the axons towards the cell bodies (‘dying-back’); (3) Demyelinating neuropathies—conditions in which the myelin sheaths are supporting Schwann cells damaged and the axons are relatively preserved. Combinations of axonal and demyelinating pathology are common. (4) Interstitial neuropathies—conditions in which there is infiltration of the endoneurium for instance by granuloma or amyloid.

Clinical features

Peripheral neuropathy characteristically causes predominantly distal muscle weakness—with or without atrophy—or sensory changes and signs of autonomic malfunction, either alone or in combination. These occur in an anatomical distribution appropriate to the nerve or nerves affected, with three broad categories recognized: (1) mononeuropathy—a lesion of an isolated peripheral nerve; (2) multifocal neuropathy/‘mononeuritis multiplex’); and (3) polyneuropathy—diffuse and bilaterally symmetrical disturbance of function, typically length-dependent.

Investigation

The diagnosis can usually be made from the history and examination. Diagnosis of both localized and generalized neuropathies may be confirmed by nerve conduction studies of motor and sensory fibres. Simple investigations for diabetes mellitus, B12 deficiency and common medical causes are sufficient for the diagnosis of many cases. Cerebrospinal fluid examination, may be useful—especially in suspected inflammatory demyelinating polyradiculopathy. When the diagnosis is not revealed by simple tests an extensive range of investigations for rare causes may be needed. Nerve biopsy is rarely required and is principally useful for the detection of vasculitis which cannot be diagnosed in any less invasive way.

Causes of peripheral neuropathies

Mononeuropathies—common conditions include median nerve compression due to carpal tunnel syndrome, and damage to the ulnar nerve at the elbow and the common peroneal nerve at the fibular head.

Generalized neuropathies—causes include (1) diabetes mellitus—most commonly producing a symmetrical sensory polyneuropathy; autonomic neuropathy may be debilitating; (2) alcohol—usually in association with thiamine deficiency (3) other metabolic/endocrine disorders—e.g. amyloidosis, uraemia, myxoedema, acromegaly, critical illness polyneuropathy; (4) toxic—including industrial/environmental substances (e.g. acrylamide, lead, thallium) and drugs (e.g. phenytoin, cisplatin, isoniazid, vincristine, thalidomide); (5) deficiencies—e.g. thiamine, vitamin B12; (6) inflammatory—e.g. Guillain–Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy, multifocal motor neuropathy, paraprotein associated neuropathy; (7) infection related—leprosy, Lyme borreliosis, HIV infection; (8) granulomatous—sarcoidosis; (9) vasculitic disorders; (10) neoplastic and paraneoplastic—most often with bronchial or ovarian malignancy; (11) genetic conditions—e.g. porphyria, familial amyloid polyneuropathy, Charcot–Marie–Tooth (hereditary motor and sensory neuropathy) disease, hereditary neuropathy with liability to pressure palsies, Refsum’s disease; and (12) chronic idiopathic axonal polyneuropathy—the cause of about 25% of cases of late onset symmetrical polyneuropathy remains unknown despite extensive investigation.

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