Nerve conduction velocity (NCV) is a test to see how fast electrical signals move through a nerve.
How the test is performed
Patches called surface electrodes, similar to those used for
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.
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 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 have muscle soreness after the test at the site of the needles.
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,
NCV is related to the diameter of the nerve and the degree of myelination (the presence of a
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results mean
Most often, abnormal results are due to some sort of nerve damage or destruction, including:
Axonopathy(damage to the long portion of the nerve cell)
- Conduction block (the impulse is blocked somewhere along the nerve pathway)
Demyelination(damage and loss of the fatty insulation surrounding the nerve cell)
The nerve damage or destruction may be due to many different conditions, including:
Alcoholic neuropathy Diabetic neuropathy
- Nerve effects of
uremia(from kidney failure)
- Traumatic injury to a nerve
Guillain-Barre syndrome Diphtheria Carpal tunnel syndrome Brachial plexopathy Charcot-Marie-Tooth disease (hereditary) Chronic inflammatory polyneuropathy Common peroneal nerve dysfunction Distal median nerve dysfunction Femoral nerve dysfunction
- Friedreich’s ataxia
General paresis Mononeuritis multiplex Primary amyloidosis Radial nerve dysfunction Sciatic nerve dysfunction Secondary systemic amyloidosis Sensorimotor polyneuropathy Tibial nerve dysfunction Ulnar nerve dysfunction
What the risks are
There are no risks.
An NCV test shows the condition of the best surviving nerve fibers, so in some cases the results may be normal even if there is nerve damage.