Nerve Conduction Test: What Is It, and Why Is It Used?
If you have certain nerve or muscle symptoms, your doctor may order a nerve conduction test. A nerve conduction velocity (NCV) test, also called a nerve conduction study, detects nerve damage. It measures the speed and strength of electrical impulses as they move down a nerve.
If the nerve is damaged or blocked, the electrical conduction will slow or weaken its transmission.
Your doctor may order an electromyogram (EMG) test in conjunction with the nerve conduction test. An EMG examines the electrical signals that your muscles make when they are at rest. NCV and EMG tests are sometimes done separately, but they are often performed together.
NCV tests diagnose nerve damage or disease. When NCV and EMG tests are performed together, the results help determine if the problem is a nerve or a muscle issue.
When the NCV test results are typical, the problem may be in the muscle and not the nerve. When the NCV test results are not typical, nerve damage is generally the origin of the issue.
Common symptoms that tend to require the NCV test are:
- muscle weakness
- tingling or numbness in the arms, legs, hands, feet, and face
- muscle cramps, spasms, and twitching
- paralysis of any of the muscles
Diseases and conditions that may require NCV testing include:
- Guillain-Barré syndrome
- Charcot-Marie-Tooth disease
- Lambert-Eaton syndrome
- amyotrophic lateral sclerosis
- myasthenia gravis
- carpal tunnel and tarsal tunnel syndromes
- myopathies, including muscular dystrophy
- spinal problems, such as herniated discs or sciatica
- neuropathies, including diabetic neuropathy and alcoholic neuropathy
- herniated disc
Neurologists typically perform nerve conduction testing. A neurologist is a highly trained doctor specializing in diagnosing, treating, and managing brain and nervous system disorders.
It is possible for physical medicine doctors and rehabilitation physicians to perform this procedure as well.
An NCV test is typically an outpatient procedure. It is performed either in your doctor’s office or a clinic setting.
During the test, your doctor will apply electrode patches to your skin. Two patches are placed directly over your nerve on the skin. One electrode will stimulate the nerve, while the other electrode records the response. This pattern is repeated for each nerve tested.
The speed of the electrical impulse is calculated by the time it takes for the response to move between the two electrodes.
If you are also having an EMG completed to measure the electrical responses of your muscles, it will be done at the same appointment, usually following the NCV test.
The risks and potential complications of NCV testing are very low. There is a small risk of disruption if you have a pacemaker or a cardiac defibrillator. However, according to some studies, disruption is rare, so this should not keep you from having the test.
It is important to let your doctor know if you have a pacemaker or a cardiac defibrillator.
In rare cases, there is also a risk of:
- nerve injury
First, tell your doctor about all medications, herbal supplements, and over-the-counter drugs that you are taking, including aspirin or nonsteroidal anti-inflammatory drugs.
Questions to ask your doctor
Some questions you may want to ask your doctor before the test include:
- Why do I need a nerve conduction test?
- What can I expect during the test?
- Will it be painful for me?
- What information will you get from a nerve conduction test?
- How many nerves do you need to test?
- How long will the test take?
- Will you also order an EMG?
- Will I need someone to drive me to the appointment?
- Will I be given any sedatives during the test?
- When can I expect the results?
- What other tests or procedures might I need?
On the day of the test
You can prepare for the test by following these steps:
- Take a bath or shower that morning to remove any lotions or oils from your skin.
- Wear comfortable, loose-fitting clothes.
- Do not use oils, lotions, moisturizers, or hair products.
- Bring a list of your medications and take them as usual unless instructed otherwise.
- Remove all jewelry.
- Tell the doctor if you are taking blood thinners or have a pacemaker.
During the test
- You will have to change into a gown.
- You will sit or lie down for the test.
- Your neurologist will locate the nerve.
- They will attach the electrodes to the skin over the nerves.
- Signals are transmitted.
- The speed and distance of the electric impulses are measured.
- Your neurologist will repeat this process for each nerve tested.
You may experience minor discomfort during the procedure.
After the test
Your doctor will give you orders regarding what activities to resume and when to return to work. However, in most cases, you can resume your activities the same day.
Here are some more questions that people have asked about nerve conduction tests. Dr. Nancy Hammond, M.D., has reviewed them.
Is a nerve conduction test painful?
The NCV test typically creates only minor discomfort.
How long does it typically take to receive the results of a nerve conduction test?
Receiving the results of your NCV test will vary depending on your doctor’s office policy. Typically, you should expect to hear back within a couple of days to a week.
What are the signs of nerve damage?
There are over 100 types of nerve damage that can affect the autonomic nerves, motor nerves, and sensory nerves. There are many different symptoms, depending on the specific nerves affected.
Here are some typical symptoms of nerve damage that people often ignore:
- daily activities becoming more complicated
- unusual sensations in the hands and feet
- changes in bodily secretions
- bowel, bladder, or sexual health changes
- a loss of muscle movement
- not feeling pain
- a loss of muscle strength
An NCV test can detect any kind of nerve damage. It is often done along with an EMG test to check for muscular damage.
After the NCV testing is complete, your neurologist will contact you with the results. If the test confirms nerve damage, your doctor will help you develop a specific treatment plan, depending on the type of nerve damage.