Alternative names
NCV
Definition
Nerve conduction velocity (NCV) is a test of the speed of conduction of impulses through a nerve.
How the test is performed
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).
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.
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.
What abnormal results mean
Most often, abnormal results are caused by some sort of neuropathy (nerve damage or destruction).