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Electromyography (EMG)

Electromyography (EMG) Introduction

Electromyography, or EMG, involves testing the electrical activity of muscles. Often, EMG testing is performed with another test that measures the conducting function of nerves. This is called a nerve conduction study. Because both tests are often performed at the same office visit and by the same personnel, the risks and procedures generally apply to both tests.

Muscular movement involves the action of muscles and nerves and needs an electrical current. This electrical current is much weaker than the one in your household wiring.

In some medical conditions the electrical activity of the muscles or nerves is not normal. Finding and describing these electrical properties in the muscle or nerve may help your doctor diagnose your condition.

EMG may aid with the diagnosis of nerve compression or injury (such as carpal tunnel syndrome), nerve root injury (such as sciatica), and with other problems of the muscles or nerves. Less common medical conditions include amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.



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Electromyography (EMG)

Carpal Tunnel Syndrome Overview

Carpal tunnel syndrome is a disease of the hand characterized by numbness, tingling, pain, and weakness. The disease typically affects the thumb, index, and middle fingers and is often particularly troublesome at night. A major nerve, specifically the median nerve, travels down the arm and enters the hand through the carpal tunnel, which is located in the central part of the wrist. In people with carpal tunnel syndrome, pressure in the carpal tunnel is higher than in unaffected people, and median nerve irritation occurs.

Many conditions can cause increased pressure within the carpal tunnel and lead to carpal tunnel syndrome. Carpal tunnel syndrome was first described with broken wrists. A broken wrist can cause bleeding and swelling within the carpal tunnel leading to increased pressure within the carpal tunnel. Most people with carpal tunnel syndrome have no identifiable cause. It affects almost 5% of the population and is most common in...

Read the Carpal Tunnel Syndrome article »



Read What Your Physician is Reading on eMedicine

EMG Evaluation of the Motor Unit: The Electrophysiologic Biopsy »

Since the measuring device has been constructed by the observer . . . we have to remember that what we observe is not nature itself but nature exposed to our method of questioning.

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