Eng Nerve Conduction Velocity Test

Overview & Description

Nerve conduction velocity testing (NCV) is used to evaluate damage or disease in peripheral nerves. In this test, electrical impulses are sent down the nerves of the arms and legs. The electrical impulse is applied to one end of a nerve. The time it takes to travel to the other end of the nerve is measured.

Who is a candidate for the test?

A nerve conduction velocity test is usually ordered to diagnose or evaluate:

nerve injury in a person who has weakness in an extremity

nerve injury or disease, as opposed to muscular injury or disease

the severity of nerve injury

the response of a nerve disease or injury to treatment

How is the test performed?

NCV testing is done by a neurologist or physiatrist. It can done in a nervestudy clinic office or at the hospital bedside, and usually takes 15 to 30minutes.

A conducting paste is placed on patches called electrodes. Arecording electrode is placed on the skin over the particular nerve inquestion. This electrode will record the activity or reaction of the nerve.Other electrodes are placed in a particular order near the first electrode.A special instrument is used to stimulate the nerves being studied bydelivering a small shock. The recording electrode records the time it takes for the shock to cause activity in the nerve.

The time is sent to a machine calledan oscilloscope. This machine can measure the response time of the nerve tostimulation. A calculation is then done on the response time and the distance between the electrodes. The electrical stimulation may be slightlyuncomfortable during the test.

Preparation & Expectations

What is involved in preparation for the test?

The healthcare provider may give instructions about how to prepare for a nerve conduction velocity test.

Results and Values

What do the test results mean?

Normal results from a nerve conduction velocity test mean that there is no evidence of damage or disease in the peripheral nerve.Nerve damage or disease may still exist despite normal NCV results. This isbecause other healthy fibers in the same nerve may show a normal reaction time.This test is often used in conjunction with electromyography (EMG) to evaluate neuromuscular abnormalities.

Abnormal results may depend on why the nerve conduction velocity test is being performed. These resultsmay indicate:

peripheral nerve injury or disease

carpal tunnel syndrome, acondition in which pressure on the median nerve in the wrist leads to pain or numbness in the fingers

poliomyelitis, a condition that affects the spinal cord

diabetic neuropathy, which is temporary or permanent nerve damage due to diabetes

herniated disc, which causes pain in the back

myasthenia gravis, a disease that causes extreme muscle weakness and fatigue

Guillain-Barre syndrome, acondition that causes nerve damage and inflammation, and muscle weakness and paralysis

damage to a nerve from trauma

nerve defects from kidneydisease or damage

chronic inflammatory polyneuropathy, which is the simultaneous malfunction of many peripheral nerves throughout the body. It can be caused by diabetes, chronic renal failure, or severe malnutrition.

metachromatic leukodystrophy, a very serious condition that causesdifficulty walking and difficulty controlling movements of the arms andlegs

Article type: xmedgeneral