Nerve conduction velocity (NCV) is the speed at which electrical impulses travel through a nerve. An NCV test is a diagnostic procedure used to identify and measure nerve injury or damage caused by a number of conditions.

Patients should ask their physician about any steps they may need to take before an NCV test. This may include refraining from using lotions and oils and avoiding products that contain caffeine or tobacco prior to the test.

NCV tests may be performed on either an inpatient or outpatient basis, depending on the nature of a patient’s illness. A NCV test is performed by placing an electrode on the skin over the nerve suspected of damage or injury. Additional electrodes are placed on the skin above the muscles affected by the nerve.

Mild electrical impulses are then sent through the electrode and into the skin. The electrodes surrounding the primary electrode record the result of the electrical impulse, which may feel like a small electric shock.

NCV is measured by the time it takes for the impulse to travel between the electrodes. The slower the velocity, the more likely it is that damage or injury to the nerve has occurred. The strength (amplitude) of the impulse may also be measured.

Results are usually available immediately after the test, although it may take a couple days before a patient receives an analysis of the results.

There are very few risks associated with NCV tests. Some patients may feel discomfort when the electrical impulses are delivered. For most patients, this is a minor annoyance although some may find it painful.

In many cases, an electromyography (EMG) is performed along with the NCV test. This procedure measures the electrical activity produced by muscles in response to nerve stimulation. An EMG may help diagnose conditions, such as neuropathy, that cause damage to muscle tissue and nerves. Together, the NCV test and EMG provide valuable information to physicians for the diagnosis and treatment of various conditions.