NERVE CONDUCTION...

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Nerve conduction te...

Definition

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

Alternative Names

NCV

How the test is performed

Patches called surface electrodes, similar to those used for ECG, are placed on the skin over the nerve at various locations. Each patch gives off a very mild electrical impulse, which stimulates the nerve.

The nerve's 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 determine the speed of the nerve signals.

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

How to prepare for the test

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

Tell your doctor if you have a cardiac defibrillator or pacemaker, as precautions may need to be taken.

How the test will feel

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.

Why the test is performed

This test is used to diagnose nerve damage or destruction. Occasionally, the test may be used to evaluate diseases of nerve or muscle, including myopathy, Lambert-Eaton syndrome, or myasthenia gravis.

Normal Values

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.

Reviewer Info: Joseph V. Campellone, M.D., Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network., 04/30/2007