NCV

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 are placed on the skin over nerves at various locations. Each patch gives off a very mild electrical impulse, which stimulates the nerve. 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. Electromyography (recording from needles placed into the muscles) is often done at the same time as this test.

How to Prepare for the Test
You must stay at a normal body temperature. Being too cold slows nerve conduction. Tell your doctor if you have a cardiac defibrillator or pacemaker. Special steps will need to be taken before the test in you have one of these devices.

How the Test will Feel
The impulse may feel like an electric shock. You may feel some discomfort depending on how strong the impulse is. You should feel no pain once the test is finished. Often, the nerve conduction test is followed by electromyography (EMG). In this test, needles are placed into a muscle and you are told to contract that muscle. This process can be uncomfortable during the test. 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. The test may sometimes be used to evaluate diseases of nerve or muscle, including myopathy, Lambert-Eaton syndrome, or myasthenia gravis.