What is nerve conduction velocity?
Also called an electroneurography, EneG, or nerve conduction study, a nerve conduction velocity (NCV) test is a measurement of the speed of conduction of an electrical impulse through a nerve. NCV can determine nerve damage and destruction.
During the test, the nerve is stimulated, usually with surface electrode patches attached to the skin. Two electrodes are placed on the skin over the nerve. One electrode stimulates the nerve with a very mild electrical impulse and the other electrode records it. The resulting electrical activity is recorded by another electrode. This is repeated for each nerve being tested.
The nerve conduction velocity (speed) is then calculated by measuring the distance between electrodes and the time it takes for electrical impulses to travel between electrodes.
A related procedure that may be performed is electromyography (EMG). An EMG measures the electrical activity in muscles and is often performed at the same time as NCV. Both procedures help to detect the presence, location, and extent of diseases that damage the nerves and muscles. Please see this procedure for additional information.
What happens during a nerve conduction velocity test?
A nerve conduction velocity procedure may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your physician's practices.
The NCV is performed by a neurologist, although a technologist may also perform some portions of the test.
Generally, a NCV procedure follows this process:
- You will be asked to remove any clothing, jewelry, hairpins, eyeglasses, hearing aids, or other metal objects that may interfere with the procedure.
- If you are asked to remove clothing, you will be given a gown to wear.
- You will be asked to sit or lie down for the test.
- A neurologist will locate the nerve(s) to be studied.
- A recording electrode will be attached to the skin over the nerve with a special paste and a stimulating electrode will be placed at a known distance away from the recording electrode.
- The nerve will be stimulated by a mild and brief electrical shock given through the stimulating electrode.
- You may experience minor discomfort for a few seconds.
- The stimulation of the nerve and the detected response will be displayed on an oscilloscope (a monitor that displays electrical activity in the form of waves).
Procedures where a nerve conduction velocity test would be used:
Treatment for the following neurological conditions may include a nerve conduction study: