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Definition
By Mayo Clinic staffElectromyography (EMG) is a diagnostic procedure to assess the health of muscles and the nerve cells that control them (motor neurons).
Motor neurons transmit electrical signals that cause muscles to contract. An EMG translates these signals into graphs, sounds or numerical values that a specialist interprets.
An EMG uses tiny devices called electrodes to transmit or detect electrical signals. During a needle EMG, a needle electrode inserted directly into a muscle records the electrical activity in that muscle.
A nerve conduction study, another part of an EMG, uses surface electrodes — electrodes taped to the skin — to measure the speed and strength of signals traveling between two or more points.
EMG results can reveal nerve dysfunction, muscle dysfunction or problems with nerve-to-muscle signal transmission.
- Ropper A, et al. Electrophysiologic and laboratory aids in the diagnosis of neuromuscular disease. In: Adams and Victor's Principles of Neurology. New York, N.Y.: McGraw-Hill; 2009. http://www.accessmedicine.com/content.aspx?aID=3641085. Accessed June 15, 2010.
- Patient information. American Association of Neuromuscular & Electrodiagnostic Medicine. http://www.aanem.org/education/patientinfo/patientInfo.cfm. Accessed June 15, 2010.
- Electromyography and nerve conduction velocities. Muscular Dystrophy Association. http://www.mda.org/publications/quest/q75ss.html. Accessed June 15, 2010.
- Peripheral nervous system and motor unit disorders: Introduction. The Merck Manuals: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec16/ch223/ch223a.html. Accessed June 16, 2010.
- Carpal tunnel syndrome fact sheet. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/carpal_tunnel/detail_carpal_tunnel.htm#115143049. Accessed June 16, 2010.
- Horowitz SH. Overview of electromyography. http://www.uptodate.com/home/index.html. Access June 16, 2010.
- Sorenson EJ (expert opinion). Mayo Clinic, Rochester, Minn. June 16, 2010.
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