A nerve conduction velocity (NCV) test — also called a nerve conduction study (NCS) — measures how fast an electrical impulse moves through your nerve. NCV can identify nerve damage.
During the test, your nerve is stimulated, usually with electrode patches attached to your skin. Two electrodes are placed on the skin over your nerve. One electrode stimulates your nerve with a very mild electrical impulse. The other electrode records it. The resulting electrical activity is recorded by another electrode. This is repeated for each nerve being tested.
The speed is then calculated by measuring the distance between electrodes and the time it takes for electrical impulses to travel between electrodes.
A related test that may be done is an electromyography (EMG). This measures the electrical activity in your muscles. It is often done at the same time as an NCV. Both tests help find the presence, location, and extent of diseases that damage the nerves and muscles.
NCV is often used along with an EMG to tell the difference between a nerve disorder and a muscle disorder. NCV detects a problem with the nerve, whereas an EMG detects whether the muscle is working properly in response to the nerve's stimulus.
Diseases or conditions that may be checked with NCV include:
Nerve conduction studies may also be done to find the cause of symptoms, such as numbness, tingling, and continuous pain.
Other conditions may prompt your healthcare provider to recommend NCV.
The voltage of the electrical pulses used during an NCV is considered very low.
Risks depend on your specific medical condition. Be sure to discuss any concerns with your healthcare provider before the procedure.
Certain factors or conditions may interfere with the results of NCV tests. This includes damage to the spinal cord, severe pain before the test, and body temperature.
Tell your healthcare provider if you have a cardiac defibrillator or pacemaker, as precautions may need to be taken.
An NCV procedure may be done on an outpatient basis, or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor's practices.
The NCV is done by a neurologist. This is a doctor who specializes in brain and nerve disorders. A technologist may also do some parts of the test.
Generally, an NCV procedure follows this process:
The paste used to attach the electrodes will be removed from your skin.
After the test, you may return to your previous activities, unless your healthcare provider advises you differently. Your healthcare provider may instruct you to avoid strenuous activities for the rest of the day.
Your healthcare provider may give you other instructions after the procedure, depending on your situation.
Before you agree to the test or the procedure make sure you know: