An electromyogram (EMG) is a medical test which is performed to measure electrical activity in the muscles at rest and during contracture. The goal of this diagnostic test is to learn more about the cause of a patient's muscle weakness or other muscle problems, and to distinguish between problems which originate in the muscles, and problems which originate in the nerves. Electromyograms can be performed at a doctor's office, clinic, or hospital using a machine known as an electromyograph, and they are outpatient procedures.
Usually, electromyogram and nerve conduction tests are performed at the same time. The electromyogram studies electrical impulses in the muscles, while a nerve conduction test studies the efficiency of the nerves when it comes to conducting electrical impulses. By looking at both results, a doctor can determine whether the nerves or the muscles are responsible for a patient's medical problem and determine the severity of a patient's condition.
In an electromyogram, electrode needles are inserted into the muscle and a reading is taken while the muscle is at rest before the patient is asked to contract the muscle so that a second reading can be taken. Some electromyograms are conducted with surface electrodes, rather than needles, if a doctor feels that needles would be invasive or unnecessary. The nerve conduction test utilizes surface electrodes, with one electrode putting out a mild electrical pulse, while the others read that pulse as it is conducted by the nerves.
This test can be slightly painful, as it does hurt to have the needles inserted. If only surface electrodes are used, the patient should not experience pain or discomfort. The results can be read on a print out which provides the information collected by the electomyograph machine used to conduct the test in a format which is easy to understand and read. Once the test is concluded, the patient can usually leave immediately, unless additional testing has been scheduled or a doctor wants to discuss the results with the patient.
The combination of electromyography and nerve conduction studies can be used to diagnose or rule out a large group of conditions related to the nervous system and the muscles. The information from these tests can also be used to monitor the progress of degenerative conditions or to determine how well a patient is responding to medication. Costs for an electromyogram vary, depending on the clinic performing the procedure, but the test is usually covered by insurance because it is a necessary diagnostic tool.