(Alternative names: EMG, Myogram)
Electromyography is a test that assesses the health of the muscles and the nerves controlling the muscles. A needle electrode is inserted through the skin into the muscle. The electrical activity detected by this electrode is displayed on an oscilloscope, and may be heard through a speaker.
After placement of the electrodes, you may be asked to contract the muscle (for example, by bending your arm). The presence, size, and shape of the wave form - the action potential - produced on the oscilloscope provide information about the ability of the muscle to respond when the nerves are stimulated.
EMG is most often used when people have symptoms of weakness and examination shows impaired muscle strength. It can help to differentiate primary muscle conditions from muscle weakness caused by neurologic disorders.