Electromyography (EMG)

What Is the Medical Definition of Electromyography (EMG)?

• Electromyography, or EMG, involves testing the electrical activity of muscles.
• Often, EMG testing is performed with another test that measures the conducting function of nerves. This is called a nerve conduction study.
• Because both tests are often performed at the same office visit and by the same personnel, the risks and procedures generally apply to both tests.
• Muscular movement involves the action of muscles and nerves and needs an electrical current. This electrical current is much weaker than the one in household wiring.
• In some medical conditions the electrical activity of the muscles or nerves is not normal. Finding and describing these electrical properties in the muscle or nerve may help the doctor diagnose the patient's condition.

What Will an EMG Test Tell You?

• EMG may aid with the diagnosis of nerve compression or injury (such as carpal tunnel syndrome), nerve root injury (such as sciatica), and with other problems of the muscles or nerves. Less common medical conditions include amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.

People usually have a small amount of discomfort during EMG testing because of pin insertion. Disposable needles are used so there is no risk of infection.

During nerve conduction studies, small electrodes are taped to the skin or placed around fingers. The patient typically experiences a brief and mild shock, which may be a bit unpleasant. Most people find it only slightly annoying.

No specific preparation is needed for the testing.

During EMG, small pins or needles are inserted into muscles to measure electrical activity. The needles are different than needles used for injection of medications. They are small and solid, not hollow like hypodermic needles. Because no medication is injected, discomfort is much less than with shots.

• The patient will be asked to contract his or her muscles by moving a small amount during the testing.
• With nerve conduction studies, small electrodes will be taped to the skin or placed around the fingers. The patient typically will experience a mild and brief tingling or shock, which may be a bit unpleasant.
• The person who administers the test will explain the procedure. Often muscle activity is monitored through a speaker during the test, which may make a popping or soft roaring noise. The EMG technician will be looking at an oscilloscope, which looks like a small TV set during the procedure.
• Testing may take 30 to 60 minutes.

If the patient is having this test in a doctor's office, he or she will be sent home following the procedure without any restriction of activities. Some people may have minor aches and pains from the testing.

The report of the testing will be sent to the doctor who ordered the test. The ordering doctor will discuss the results with the patient or the doctor.