Nerve Conduction Velocity (NCV)

An NCV test is recommended to patients who present with the following conditions/symptoms:

• Tingling sensation or weakness in legs
• Weakness in muscles of the lower part of the leg and foot
• Pain or numbness in fingers
• Radiating pain, numbness or tingling sensation from buttocks to lower legs
• Radiating pain, numbness or tingling sensation from shoulders or neck to arms
• Weakness, pain, tingling sensation or numbness in any other area of the body
• Autoimmune diseases that could affect the nervous system

Also, your doctor may perform this test to see the side effects of any other condition in your body or monitor an ongoing treatment such as chemotherapy.

Extensive preparations are not needed for this test. Inform your doctor if you have any medical devices implanted in your body such as a pacemaker. Also, your doctor should know about any medicines, such as blood thinners, or any medical supplements if you are taking any. No lotion or moisturiser should be applied on the skin for 2-3 days before the test. Wear comfortable clothing for the test to ensure easy access to the testing area.

This procedure is performed by a neurologist or a technician. The steps mentioned below are usually followed:

• You'll have to remove any metal objects, such as jewellery, glasses, hearing aids or hairpins before going for this test
• A hospital gown is usually worn for the test, though it may be performed in regular clothes
• Next, you'll be asked to lie down, and a neurologist will locate the nerve that needs to be checked
• He/she will then stick electrodes on your skin at the area of the test. One electrode provides stimulation, and the other records the conduction
• The recording electrode is placed at a specific distance from the stimulating one so the conduction speed can be calculated

Stimulation applied by the electrode might feel like a little stinging sensation or a mild shock, but this sensation will go away when the test is completed.

The responses from the recording electrode are seen on a screen, and the results are reported accordingly.
Normal body temperature should be maintained during the test, as a change in temperature may interfere with results.

Normal results: Results of an NCV test are generally given as metres/second (m/s). There are distinct values for nerves depending on the area of the body. Normal values for motor nerves of some of the common sites in adults are given in the table below. Values for newborns and children up to 3-4 years of age are about one-half compared to adults.