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Nerve biopsy

Definition

A nerve biopsy is the removal of a small piece of a nerve for examination.

Alternative Names

Biopsy - nerve

How the test is performed

The sural nerve (in the ankle), or the superficial radial nerve (wrist) are the sites most often used for biopsy. A local anesthetic is used to numb the area. A small incision is made, and a portion of the nerve is removed. The sample is then examined using either a regular (light) microscopic or an electron microscope. Individual nerve fibers may also be examined.

How to prepare for the test

There is no special preparation.

How the test will feel

The amount of pain during and after the procedure depends on the patient. Because a local anesthetic is used, discomfort during the procedure is usually minimal. The anesthetic may burn or sting when first injected. After the procedure, the area may feel tender or sore for a few days.

Why the test is performed

Nerve biopsy may be done to help diagnose:

• Axon degeneration (destruction of the axon portion of the nerve cell)
• Damage to the small nerves
• Demyelination (destruction of parts of the myelin sheath covering the nerve)
• Inflammatory nerve conditions (neuropathies)

Normal Values

There is normal nerve anatomy, with no abnormal growths or inclusions.

What abnormal results mean

Conditions or disorders that may be revealed include:

• Amyloidosis (sural nerve biopsy is most often used)
• Demyelination
• Inflammation of the nerve
• Leprosy
• Loss of axon tissue
• Metabolic neuropathies
• Necrotizing vasculitis
• Sarcoidosis

Additional conditions under which the test may be performed:

• Alcoholic neuropathy
• Axillary nerve dysfunction
• Brachial plexopathy
• Charcot-Marie-Tooth disease (hereditary)
• Common peroneal nerve dysfunction
• Distal median nerve dysfunction
• Mononeuritis multiplex
• Mononeuropathy
• Necrotizing vasculitis
• Neurosarcoidosis
• Radial nerve dysfunction
• Tibial nerve dysfunction

What the risks are

• Allergic reaction to the local anesthetic
• Discomfort after the procedure
• Infection (a slight risk any time the skin is broken)
• Permanent nerve damage (uncommon; minimized by careful site selection)

Special considerations

Nerve biopsy is invasive and is useful only in certain circumstances. These include diagnosis of asymmetric and multifocal nerve disorders, conditions in which a nerve enlargement can be felt with the fingers, and suspected inherited pediatric nerve disorders.

References

Shy ME. Peripheral neuropathies. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier. 2007: chap 446.