EMG/Nerve Conduction

EMG/Nerve Conduction

What is it?
Electromyography (EMG) is a test of a muscle’s electrical activity. It is used to test how a muscle responds to signals from the nerves responsible for muscle movement, called motor nerves. An EMG may also include a test of how fast the motor nerve conducts impulses. This is called a nerve conduction study (NCS) or nerve conduction velocity (NCV) test.

Who needs this procedure?
An EMG is ordered when patients have symptoms such as muscle weakness, stiffness, or atrophy. This test is often used to diagnose muscle and nerve disorders such as amyotrophic lateral sclerosis (ALS), myasthenia gravis, muscular dystrophy, myotonia, neuropathies, and myopathies. NCV is used to help make a diagnosis when the primary symptoms involve sensations such as pain, tingling, and numbness, rather than weakness.

How do I prepare for this procedure?
Your doctor will advise you not to take any stimulant drugs, drink beverages like coffee, tea, or cola, or take any medication that has a sedating effect for at least 24 hours before the test. Also, the patient should come with clean skin, free of any lotions or moisturizers. Make sure your doctor knows of any heart conditions such as a pacemaker, which could be affected by the small electrical impulses sent to the nerve during a nerve conduction velocity (NCV) test. Also make your doctor aware if you are taking any blood thinning medication (anticoagulants) or if you have a bleeding disorder because fine needles are inserted into the muscles to conduct the electrical impulse.
  
How is this procedure performed?
You will most likely put on a hospital gown to provide easy access to the areas being tested. Then you will be put into a position in which the muscle being tested is at rest, either lying down or sitting. You may feel some discomfort as a very fine needle is inserted into the muscle being tested. The needle is an electrode, which will transmit the muscle’s electrical activity to a recording device. The physician will direct you to move the muscle in various ways to tighten and relax it. The muscle’s response to movement and rest is recorded so your doctor can study the pattern for normal or abnormal electrical activity. If you are also having an NCV test, a very small electrical shock is delivered to the nerve through an electrode that transmits the nerve’s response to the recording device. An EMG takes anywhere from 30 to 90 minutes.

What can I expect after the procedure?
You may feel some soreness or notice some bruising in the muscles tested for a few days after an EMG. There may also be some minor bleeding around the needle insertion points for a few hours after the test. Notify your doctor if these conditions do not improve within these time frames.