Electromyography

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Electromyography

EMG; Myogram; Electromyogram

There is normally very little electrical activity in a muscle while at rest. Inserting the needles can cause some electrical activity, but once the muscles quiet down, there should be little electrical activity detected.

When you flex a muscle, activity begins to appear. As you contract your muscle more, the electrical activity increases and a pattern can be seen. This pattern helps your doctor determine if the muscle is responding as it should.

An EMG can detect problems with your muscles during rest or activity. Disorders or conditions that cause abnormal results include the following:

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• Alcoholic neuropathy
• Amyotrophic lateral sclerosis (ALS)
• Axillary nerve dysfunction
• Becker's muscular dystrophy
• Brachial plexopathy
• Carpal tunnel syndrome
• Cervical spondylosis
• Common peroneal nerve dysfunction
• Denervation (reduced nerve stimulation of a muscle)
• Dermatomyositis
• Distal median nerve dysfunction
• Duchenne muscular dystrophy
• Facioscapulohumeral muscular dystrophy (Landouzy-Dejerine)
• Familial periodic paralysis
• Femoral nerve dysfunction
• Friedreich's ataxia
• Guillain-Barre syndrome
• Lambert-Eaton syndrome
• Mononeuritis multiplex
• Mononeuropathy
• Myopathy (muscle degeneration caused by a number of disorders, including muscular dystrophy)
• Myasthenia gravis
• Peripheral neuropathy
• Polymyositis
• Radial nerve dysfunction
• Sciatic nerve dysfunction
• Sensorimotor polyneuropathy
• Shy-Drager syndrome
• Thyrotoxic periodic paralysis
• Tibial nerve dysfunction
• Ulnar nerve dysfunction

Review Date: 08/27/2010
Reviewed By: Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).