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Stimulation Myelographic Study - Nerve Conduction Velocity Test
Overview & Description
Nerve conduction velocity testing (NCV) is used to evaluate damage or disease in peripheral nerves. In this test, electrical impulses are sent down the nerves of the arms and legs. The electrical impulse is applied to one end of a nerve. The time it takes to travel to the other end of the nerve is measured.
Who is a candidate for the test?
A nerve conduction velocity test is usually ordered to diagnose or evaluate:
How is the test performed?
NCV testing is done by a neurologist or physiatrist. It can done in a nerve study clinic office or at the hospital bedside, and usually takes 15 to 30 minutes.
A conducting paste is placed on patches called electrodes. A recording electrode is placed on the skin over the particular nerve in question. This electrode will record the activity or reaction of the nerve. Other electrodes are placed in a particular order near the first electrode. A special instrument is used to stimulate the nerves being studied by delivering a small shock. The recording electrode records the time it takes for the shock to cause activity in the nerve.
The time is sent to a machine called an oscilloscope. This machine can measure the response time of the nerve to stimulation. A calculation is then done on the response time and the distance between the electrodes. The electrical stimulation may be slightly uncomfortable during the test.
Preparation & Expectations
What is involved in preparation for the test?
The healthcare provider may give instructions about how to prepare for a nerve conduction velocity test.
Results and Values
What do the test results mean?
Normal results from a nerve conduction velocity test mean that there is no evidence of damage or disease in the peripheral nerve. Nerve damage or disease may still exist despite normal NCV results. This is because other healthy fibers in the same nerve may show a normal reaction time. This test is often used in conjunction with electromyography (EMG) to evaluate neuromuscular abnormalities.
Abnormal results may depend on why the nerve conduction velocity test is being performed. These results may indicate:
Attribution
Author:Eileen McLaughlin, RN, BSN
Date Written:
Editor:
Edit Date:
Reviewer:Gail Hendrickson, RN, BS
Date Reviewed:
Sources
Mosby's Manual of Diagnostic and Laboratory Tests, 1998
Illustrated Guide to Diagnostic Tests, Springhouse, 1998