Nerve Conduction Study

Nerve conduction velocity (NCV) is a test of the speed of conduction of impulses through a nerve.

The nerve is stimulated, usually with surface electrodes, which are patch-like electrodes (similar to those used for ECG) placed on the skin over the nerve at various locations. One electrode stimulates the nerve with a very mild electrical impulse.

The resulting electrical activity is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to calculate the nerve conduction velocity.

Electromyography is often done at the same time as the NCV test.

Normal body temperature must be maintained (low body temperature slows nerve conduction).

The impulse may feel like an electric shock. Depending on how strong the stimulus is, you will feel it to varying degrees, and it may be uncomfortable you. You should feel no pain once the test is finished.

Often the nerve conduction test is followed by electromyography (EMG) which involves needles being placed into the muscle and you contracting that muscle. This can be uncomfortable during the test, and you may feel muscle soreness at the site of the needles afterwards as well.

This test is used to diagnose nerve damage or destruction.

NCV is related to the diameter of the nerve and the normal degree of myelination (the presence of a myelin sheath on the axon) of the nerve. Newborn infants have values that are approximately half that of adults, and adult values are normally reached by age 3 - 4.

Most often, abnormal results are caused by some sort of neuropathy (nerve damage or destruction) including:

• Demyelination (destruction of the myelin sheath)

• Conduction block (the impulse is blocked somewhere along the nerve pathway)

• Axonopathy (damage to the nerve axon)

Some of the associated diseases or conditions include:

• Alcoholic neuropathy

• Diabetic neuropathy

• Nerve effects of uremia (from kidney failure)

• Traumatic injury to a nerve

• Guillain-Barre syndrome

• Diphtheria

• Carpal tunnel syndrome

• Brachial plexopathy

• Charcot-Marie-Tooth disease (hereditary)

• Chronic inflammatory polyneuropathy

• Common peroneal nerve dysfunction

• Distal median nerve dysfunction

• Femoral nerve dysfunction

• Friedreich's ataxia

• General paresis

• Lambert-Eaton Syndrome

• Mononeuritis multiplex

• Primary amyloid

• Radial nerve dysfunction

• Sciatic nerve dysfunction

• Secondary systemic amyloid

• Sensorimotor polyneuropathy

• Tibial nerve dysfunction

• Ulnar nerve dysfunction

Any peripheral neuropathy can cause abnormal results, as can damage to the spinal cord and disk herniation (herniated nucleus pulposus) with nerve root compression.

What the risks are   

Special considerations