Nerve Conduction Velocity study / Electromyography
NCV/EMG is a suite of measurements that a doctor may order to assist in making the right diagnosis for a medical condition. They are usually ordered when a patient is having problems with their muscles or nerves. This may include a pinched nerve in the back or the neck, tingling or numbness in arms or legs, or carpal tunnel syndrome. Many other medical problems might suggest the need for the test. If you have any questions as to why you might need the test, ask your doctor.
The suite has two main components. The first is a nerve conduction study which is used to evaluate the electrical conduction of motor and sensory nerves. One common measurement made in a study is the Nerve Conduction Velocity – hence this part of the suite is often referred to as “NCV”. The second main component is Electromyography (EMG) – a technique for recording and evaluating the electrical activity produced by skeletal muscles.
An EMG is done to:
Find diseases that damage muscle tissue, nerves, or the junctions between nerve and muscle. These problems may include a herniated disc, amyotrophic lateral sclerosis (ALS), or myasthenia gravis (MG). Find the cause of weakness, paralysis, or muscle twitching. Problems in a muscle, the nerves supplying a muscle, the spinal cord, or the area of the brain that controls a muscle can cause these symptoms. The EMG does not show brain or spinal cord diseases. An EMG may take 30 to 60 minutes.
A nerve conduction study is done to:
Find damage to the peripheral nervous system, which includes all the nerves that lead away from the brain and spinal cord and the smaller nerves that branch out from those nerves. This test is often used to help find nerve problems such as carpal tunnel syndrome or Guillain-Barré syndrome. Nerve conduction studies are done before an EMG if both tests are being done. Nerve conduction tests may take from 15 minutes to 1 hour or more, depending on how many nerves and muscles are studied.
An EMG/NCV is done in the doctor’s office. It may be done in a room that stops any outside electrical interference. You will be asked to put on a gown and lie on a bed so your muscles are relaxed.
These tests may be completed in our Sacramento offices with our technologists and supervising Neurologist. Our technologists and equipment also “go-mobile” to provide services to medical practices throughout Northern California.
How to prepare for a NCV/EMG
- Bring a list of medications you are currently taking.
- On the day of the test, take a shower to remove body oil and do not use any body lotions.
Before the tests begin, inform the technologists if:
- You have a cardiac pacemaker, electrical stimulator, or other electrical device.
- You have any bleeding problems or are taking blood thinning medications.
- You have allergies.
Otherwise, few preparations are needed. For these tests there is no special fasting or eating required. The tests do not have to be done at any special time of day. Driving home from the test would be as usual as driving home from a dentist visit. You can resume regular activities after the test is over.
How long does the test take?
Allow at least one hour in the examination room if just one extremity is being tested. Allow more time if more extremities need to be tested.
What does the test feel like?
For the nerve conduction study a low voltage electrical current is pulsed at the surface of the skin for a split second. There may be a strong tingling feeling and a twitching of muscles.
For the electromyography there is a quick sharp pain as a needle is put into a muscle. The thin fine needle does not inject anything or even send any electricity into the muscle. It is only a recording device. Once in the muscle, the sensation may be discomfort or pressure.