Electromyogram, or EMG
An electromyogram, or EMG, is a test that measures the activity of the muscles. The test gathers information about the muscular and nervous systems.
An EMG is a way of finding causes of muscle weakness or paralysis; muscle problems such as muscle twitching; numbness, tingling or pain; and nerve damage or injury.
An EMG can be done in a doctor's office, hospital or lab by a nurse, doctor, or x-ray technician.
How do I get ready for this test?
Before having an EMG, you will be told not to use body lotions for several days before testing, not to smoke for twenty-four hours before the test, and to avoid coffee, tea or other drinks with caffeine for three hours before the test.
What are the benefits? What are the possible side effects?
EMG has many benefits:
- the results are safe and reliable,
- side effects are rare,
- there is no risk of allergic reaction,
- the test is generally fast, and
- it is fairly inexpensive.
Infection after EMG is rare, but if it does happen, symptoms may be increasing pain, redness, swelling, tenderness, or yellowish-white pus.
You should let your doctor know you have a pacemaker, any bleeding problems, any allergies, or if you have taken or are now taking any medicines. If you don't tell the doctor or nurse, you may have problems with the test.
How is an EMG done?
The EMG takes thirty to sixty minutes, depending on the number of muscles to be tested. A small metal needle is inserted through the skin into the muscles to record impulses or electrical activity in the muscle. The doctor will read the EMG when your muscle is resting, when it is contracting slightly (for example, by bending your arm), and when it is contracting with more force.
The needle or electrode position may be changed and the process repeated four or more times in the same muscle for a more complete study.
The results are studied to determine the cause of the muscle problem.
At the same time as the EMG, you may also have a nerve conduction velocity (NCV) test to rule out disorders of the nerve or nerve injuries that may be affecting the muscles. For this test, electrodes are placed on the skin to measure the activity of the nerves.
If you are extremely nervous, you may be given a sedative before the EMG test.
Will it hurt?
Some people report feeling discomfort or pain, depending on the muscles being tested.
After the test, you may have mild aching for up to six hours, followed by soreness and tingling in the muscle that was tested for one or two days. You may also have a small bruise that lasts for a week or more.
If pain lasts longer than two days, put heat on the test site by making a warm compress. Do this by soaking a small towel or washcloth in warm water and applying it to the painful area. Be careful not to make the compress too hot, so you don't burn your skin. Be sure to let your doctor know if you have severe or long-lasting pain.
Watch a video of an EMG.
Updated March 2012