What is a nerve conduction velocity test?

A nerve conduction velocity test (NCV) is an electrical  test that is used to determine the adequacy of the conduction of the nerve  impulse as it courses down a nerve. This test is used to detect signs of nerve  injury.

In this test, the nerve is electrically stimulated, and  the electrical impulse down stream from the stimulus is measured. This is  usually done with surface patch electrodes (they are similar to those used for  an electrocardiogram) that are 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 speed of impulse  transmission (nerve conduction velocity). A decreased speed of transmission  indicates nerve disease. A nerve conduction velocity test is often done at the  same time as an electromyogram (EMG) in order to exclude or detect muscle  conditions.

When is a nerve conduction velocity test used?

Symptoms that might prompt a health care professional to  order an nerve conduction velocity test test include numbness, tingling, and/or burning sensations. The  nerve conduction velocity test  test can be used to detect true nerve disorders (such as peripheral neuropathy  and mononeuritis multiplex) or conditions whereby nerves are affected by mechanical compression injury  (such as carpal tunnel syndrome and compression neuropathy). A normal body temperature must be maintained for the  nerve conduction velocity test, because low body temperatures slow nerve conduction.