Site Map

Nerve conduction velocity

NCV

Nerve conduction velocity (NCV) is a test to see how fast electrical signals move through a nerve. This test is done along with electromyography (EMG) to assess the muscles for abnormalities.

Images

Nerve conduction test

I Would Like to Learn About:

How the Test is Performed

Adhesive patches called surface electrodes are placed on the skin over nerves at different spots. Each patch gives off a very mild electrical impulse. This stimulates the nerve.

The resulting electrical activity of the nerve 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 measure the speed of the nerve signals.

EMG is the recording from needles placed into the muscles. This 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 or too warm alters nerve conduction and can give false results.

Tell your doctor if you have a cardiac defibrillator or pacemaker. Special steps will need to be taken before the test if you have one of these devices.

Do not wear any lotions, sunscreen, perfume, or moisturizer on your body on the day of the test.

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, a needle is 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 or bruising after the test at the site where the needle was inserted.

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:

Normal Results

NCV is related to the diameter of the nerve and the degree of myelination (the presence of a myelin sheath on the axon) of the nerve. Newborn infants have values that are approximately half that of adults. Adult values are normally reached by age 3 or 4.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.

What Abnormal Results Mean

Most often, abnormal results are due to nerve damage or destruction, including:

The nerve damage or destruction may be due to many different conditions, including:

Any peripheral neuropathy can cause abnormal results. Damage to the spinal cord and disk herniation (herniated nucleus pulposus) with nerve root compression can also cause abnormal results.

Considerations

An NCV test shows the condition of the best surviving nerve fibers. Therefore, in some cases the results may be normal, even if there is nerve damage.

Related Information

Osmotic demyelination syndrome
Mononeuropathy
Alcoholic neuropathy
Diabetes and nerve damage
Prerenal azotemia
Acute kidney failure
Guillain-Barré syndrome
Diphtheria
Carpal tunnel syndrome
Brachial plexopathy
Charcot-Marie-Tooth disease
Chronic inflammatory demyelinating polyneuropathy
Common peroneal nerve dysfunction
Distal median nerve dysfunction
Femoral nerve dysfunction
General paresis
Lambert-Eaton syndrome
Multiple mononeuropathy
Primary amyloidosis
Radial nerve dysfunction
Sciatica
Secondary systemic amyloidosis
Sensorimotor polyneuropathy
Tarsal tunnel syndrome
Ulnar nerve dysfunction
Peripheral neuropathy
Herniated disk

References

Deluca GC, Griggs RC. Approach to the patient with neurologic disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 368.

Nuwer MR, Pouratian N. Monitoring of neural function: electromyography, nerve conduction, and evoked potentials. In: Winn HR, ed. Youmans and Winn Neurological Surgery. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 247.

BACK TO TOP

Review Date: 4/21/2019  

Reviewed By: Amit M. Shelat, DO, FACP, FAAN, Attending Neurologist and Assistant Professor of Clinical Neurology, Stony Brook University School of Medicine, Stony Brook, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

ADAM Quality Logo

A.D.A.M., Inc. is accredited by URAC, for Health Content Provider (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics. This site complies with the HONcode standard for trustworthy health information: verify here.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- 2019 A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

A.D.A.M. content is best viewed in IE9 or above, Firefox and Google Chrome browser.