A Nerve Conduction Velocity Test: How Does It Work & What is it Used For?

A nerve conduction velocity (NCV) test is a commonly used diagnostic test to check for nerve damage and dysfunction.^(1,2,3) The procedure measures the speed at which electrical signals move through your peripheral nerves. Peripheral nerves are located along the spinal cord and outside the brain. The peripheral nerves help control the muscles and are also responsible for letting you experience the senses. Healthy nerves of the body will send electrical signals more quickly and also with greater strength than damaged nerves.^(4,5,6)

A nerve conduction velocity test lets your doctor differentiate between an injury caused to the myelin sheath, which is the protective covering that surrounds the nerve, or an injury to the nerve fiber. The test can also help your doctor differentiate between a nerve disorder and a condition where the muscles have been affected by a nerve injury.⁽⁷⁾

Being able to differentiate between these conditions is important for your doctor to make a proper diagnosis of your condition and determine the proper course of treatment.

During the test, a nerve is directly stimulated with electrical currents to check its reaction. This diagnostic test is often used by doctors to diagnose a wide variety of muscular and neuromuscular conditions. Usually, to narrow down the diagnosis, doctors may use the nerve conduction velocity test in combination with electromyograms (EMGs). An electromyogram is used to detect whether a muscle is responding correctly to the nerve signals, helping doctors determine whether a person has a muscle condition or a nerve disorder.⁽⁸⁾

A nerve conduction velocity test can be used for diagnosing a variety of muscular and neuromuscular disorders, including:

• Carpal tunnel syndrome⁽⁹⁾
• Guillain-Barre syndrome⁽¹⁰⁾
• Sciatic nerve problems
• Peripheral nerve injury⁽¹¹⁾
• Charcot-Marie-Tooth (CMT) disease⁽¹²⁾
• Chronic inflammatory neuropathy and polyneuropathy⁽¹³⁾
• Herniated disk disease

If your doctor suspects a pinched nerve, in that case, also a nerve conduction velocity test will be recommended, sometimes in combination with electromyography.

Before scheduling your nerve conduction velocity test, your doctor will ask detailed questions about any existing conditions, medications you are taking, or behaviors that may have a possible impact on the rest of the test. These may include:

• Diabetes
• Hypothyroidism
• Alcohol abuse
• Systemic diseases
• Use of certain neurologic medications like opioids, muscle relaxants, or psychotropic medications.

You need to also inform your doctor if you have a pacemaker. This is because the electrodes used in the nerve conduction velocity test can have an effect on the electronic impulses of the pacemaker.

A couple of days before you are scheduled to take the test, you should stop using any oils or lotions on your skin. This is because the creams can prevent the electrode from getting properly placed onto the skin. While you do not need to fast before the test, but you may be told you avoid taking caffeine before the test.

While the exact particulars of nerve conduction velocity tests can vary from person to person, but they follow a similar general process. Here’s what you should expect during the test:

1. You will need to remove any metallic objects on you, including jewelry, as that could interfere with the test and results.
2. You will be asked to remove some clothing and put on a gown.
3. You will then be instructed to either sit or lie down for the test.
4. Your doctor will put two electrodes on your skin. One of the electrodes will stimulate the nerve, and the second one will record the stimulation. Your doctor is likely to use some kind of paste or gel to help the electrodes stick to your skin.
5. The test will stimulate the nerve with a mild and brief electrical shock that will come from the stimulating electrode. For example, one standard test stimulates the nerves in the finger and records the stimulus with the electrode placed near the wrist.

The entire NCV test is going to take around 20 to 30 minutes. You may find the stimulating sensation to be uncomfortable, but it is usually not painful.

Depending on the exact reason why you are having NCV test, your doctor is likely to perform this test in more than one location on the body. In a 2009 study, researchers used the nerve conduction velocity test to look at the damage caused to the ulnar nerve. The ulnar nerve is responsible for providing sensation to the hands and feet. When the researchers added a third stimulation site to the usual two sites used, it increased the sensitivity of the nerve test from 80 to 96 percent.⁽¹⁴⁾

Once you are done with the test, your doctor and the specialist who carried out the test will let you know when or if you need to get the test done again.

One of the biggest advantages of the nerve conduction velocity test is that it is considered to be an accurate, objective measurement of the health of a nerve as compared to other subjective reports of poor functioning and pain. ⁽¹⁵⁾ A nerve conduction velocity of 50 to 60 meters per second is considered to be within the normal range.

Any result you get also has to be examined together with other information. For example, your doctor will compare your results against a standard of conduction velocities, and it is important to note that there is no one standard of conduction velocities. The results are also affected by various factors, including your age, what part of the body the electrodes have been placed on, your gender, and sometimes even where you live.

A conduction velocity that falls outside of the standard indicates that there is damage to the nerve or the nerve is diseased. However, the velocity does not indicate what caused this damage. A wide variety of conditions can affect a nerve, causing the conduction velocity to fall outside of the norm. These include:

• Diabetic neuropathy
• Carpal tunnel syndrome
• Chronic inflammatory polyneuropathy
• Acute inflammatory polyneuropathy
• Peripheral nerve injury
• Traumatic median nerve damage
• Drug-induced median nerve palsy
• Sciatic nerve problems
• Guillain-Barre syndrome
• Herniated disk disease
• Pinched nerves
• Damage from cancer drugs
• Charcot-Marie-Tooth disease

Your final diagnosis also depends on many other information in your family and medical history, as well as your physical symptoms. It is important to understand that there is no one path to recovery from a diseased or damaged nerve. The treatment for your condition will depend on the underlying cause and which nerve is affected.

Recovery from nerve damage or diseased nerves is often lengthy and can be painful. Your age at the time of the injury plays a very important part in determining your recovery. A nerve that is damaged at a very young age will react in a different manner than a nerve that gets affected later in life. In some cases, nerve damage resulting from a childhood injury might not become apparent until adolescence or much later in life.

Furthermore, the severity and length of an injury also make a difference in your outlook. Sustained trauma may cause irreversible or long-term nerve damage, while a shorter exposure to the same injury could be reversed with rest and treatment.

In case of severe nerve damage, you may need to be treated with nerve grafts, and there is a lot of research going on about using cultured cells to promote regrowth of the damaged or diseased nerve.

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