Electromyography (EMG) is a test that is used to record the electrical activity of muscles. An EMG is a graphic record of the study, and can also be referred to as a myogram. When muscles are active, they produce an electrical current. This current is usually proportional to the level of the muscle activity.

An EMG is most often performed when patients have muscle pain, tingling, numbness, or weakness. The EMG helps to distinguish between muscle conditions in which the problem begins in the muscle and muscle weakness due to nerve disorders. The EMG can also be used to detect true weakness, as opposed to weakness from reduced use because of pain or lack of motivation.

EMG's can be used to detect abnormal electrical muscle activity that can occur in many diseases and conditions, including muscular dystrophy, inflammation of muscles, pinched nerves, peripheral nerve damage (damage to nerves in the arms and legs), amyotrophic lateral sclerosis (ALS) (also known as Lou Gehrig disease), myasthenia gravis, disc herniation, and others.

Electrodiagnostic medicine studies the diseases or abnormalities of the nerves and muscles.  A patient can have problems with nerves and muscles in only one part of their body or throughout their entire body. Some of the tests used to diagnose symptom are nerve conduction studies (NCS) and needle electromyography (EMG.)

Nerve Conduction Studies

NCS show how well the body’s electrical signals are traveling in a nerve. It is done by applying small electrical shocks to the nerve and recording how the nerve works. These shocks cause a quick, mild, tingling feeling. The doctor may test several nerves.

Needle Electromyography

For this part of the exam, a small, thin needle is inserted into several muscles. There may be some minor pain when the needle is inserted. The doctor will look and listen to the electrical signals that travel from the muscle to the EMG monitor.

The results of these tests will help the doctor evaluate what is wrong and how best to treat a patient. These tests usually take approximately 30 minutes.