Electromyography (EMG) is an electrodiagnostic test that measures the nerve impulses in muscles during contraction. Nerves throughout the body exchange information with the brain through nerve impulses. Healthy muscles need nerve input to perform movements. Doctors use EMG to identify muscle function as related to nerve input. EMGs help doctors diagnose neuromuscular disease, neurological disorders, muscle disease, and nerve abnormalities associated with pain or numbness.
EMGs are usually outpatient electrodiagnostic procedures. EMGs can take place at a doctor's office or in a hospital. The nerve test typically lasts 30 to 60 minutes.
To begin, your doctor will place fine needle electrodes through the skin and into the muscles that a nerve controls. The electrodes transmit information about the nerve/muscle electrical activity. A computer records nerve impulses while the muscle is at rest and during muscle movement.
The examiner may reposition the electrodes throughout the test. More than one muscle is typically tested. Your doctor will share the results with you.
An EMG may be uncomfortable during the test. Your muscles may remain a bit sore following the procedure.
It is common for an EMG and another type of nerve test, nerve conduction velocity (NCV), to take place at the same time. The NVC usually precedes the EMG.