An electromyogram (EMG) is a diagnostic test that measures the electrical activity of the muscle in the body. It is often used diagnostically to determine the cause of muscle weakness and decreased muscle strength. It may also be used to differentiate muscle weakness caused by injured nerves and weakness due to neurological disorders. An electromyogram can help to diagnose certain nerve and muscle disorders that cause weakness, numbness, paralysis, or twitching of the muscles.
The Electromyogram Procedure
An EMG uses very small devices called electrodes to transmit or detect electrical signals. A very thin needle electrode is inserted through the skin into the muscle. After placement of the electrodes, the electrical activity will first be recorded of the muscles at rest. Patients may then be asked to contract the muscles and the resulting electrical activity will be recorded. The electrodes might be moved to different muscles or different areas of the muscles during the EMG. The electrical activity of the muscles is displayed on a video monitor, as the electrodes on the needle pick up the electrical activity given off by the muscles. The electrical activity recorded on the monitor provides information about the muscle's ability to respond when the nerves of the muscles are stimulated.
The EMG procedure is considered safe with very few risks, and complications are rare. There is a small risk of bleeding, infection and nerve injury, in the area where the needle electrode was inserted. After reviewing the results of the EMG, a doctor can make an appropriate diagnosis.