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Electromyography

What is an EMG?

Electromyography (EMG) is a diagnostic test used to detect muscle disorders and evaluate the functioning of your muscles. An EMG is designed to record the electrical activity produced by the muscles during rest and contraction.

Your doctor may arrive at a diagnosis based on the results of the EMG along with information from your medical history, physical and neurological examinations, and results from other tests.

Indications of EMG

EMG testing can be used for the diagnosis of various disorders that damage muscle tissue, nerves, or the junctions between nerve and muscle, such as a herniated disc, amyotrophic lateral sclerosis (ALS) or myasthenia gravis (MG). An EMG can also be used to evaluate the cause of weakness, paralysis and muscle twitching.

Contraindications of EMG

EMG is generally a safe procedure. However, certain factors or conditions may interfere with the test results. These tests are usually avoided in individuals with swelling, bleeding, or obesity and those taking medications, such as skeletal muscle relaxants and anticholinergics.

Instructions given before EMG

Your physician may advise you to stop certain medicines, like blood thinners, 3 to 6 days prior to your procedure. Inform your doctor if you have a pacemaker implanted. You will be instructed not to smoke, eat or drink foods that contain caffeine for 3 hours before the test.

EMG procedure

Electromyography is performed by an EMG technologist or a doctor. It may be conducted in a doctor's office, hospital or clinic. During the test, you will be asked to sit on a reclining chair or lie down on a table or bed so that the muscles being tested are relaxed. The skin over the test site is cleansed and a needle electrode is inserted into the muscle, connected by wires to a recording machine. You may feel a quick, sharp pain during the insertion of the electrode. Your doctor then records your readings with the muscle at rest and under contraction. The needle electrode may be moved several times to record the electrical activity in different areas of the muscle.

On the computer screen, the electrical activity may be depicted as wavy and spiky lines. Electrical impulses may also be monitored through a speaker, in which the electrical signals are denoted by a popping sound or monitored on video.

After the test, the needle electrode is removed and your skin is cleansed. An EMG normally takes about 30 to 60 minutes.

Post EMG

Pain medications are given if you experience any soreness at the site of needle insertion. Some soreness and a tingling sensation may persist for 1 or 2 hours after electromyography. Call your doctor, if you experience increasing pain, swelling, tenderness or pus at any of the needle insertion sites.

Affiliations

  • Texas Orthopedic Hospital
  • Joe W. King Orthopedic Institute
  • American Academy of Orthopaedic Surgeons
  • The American Board of Orthopaedic Surgery