Electromyography (EMG) is an examination, in which the functioning of muscles and nerves is measured by stimulating the nerves. Thus, defects can be determined in muscles and nerves. The registration of this examination takes place in the form of a graph, the electromyogram.
Electromyography is used to detect defects in the muscle function, in the nerve controlling the muscle or in the transition between the nerve and the muscle. It is helpful in the diagnosis of diseases, such as muscular dystrophy and other muscle diseases, peripheral neuropathies, polio, radiculopathies and Guillain-Barré syndrome. The examination also contributes to determining the damage in case of paralysis, caused by spinal cord injury.
When a muscle contracs, the muscle sends out an electrical signal. These signals can be measured with electrodes. The electrodes pick up the electrical signals and send them to an oscilloscope. The oscilloscope converts the signals into a graph. This graph provides information on the functioning of the muscle and the nerve.
There are two types of electromyography: conduction study and needle study.
In a conduction study, electrodes are stuck to the skin. Several electrodes can be applied at different places. The nerve is stimulated at various locations, making the hand or foot move.
In the needle study, special needles are stung into the muscle. Those needles contain electrodes. The patient is asked to tighten the muscles a few times.
An electromyography can sometimes be painful, but afterwards there are no symptoms. The examination takes about 30 minutes.