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EMG Nerve Test Information

written by: Leigh A. Zaykoski•edited by: Leigh A. Zaykoski•updated: 6/30/2009

The EMG nerve test is often done to diagnose disorders that can cause damage to or weakness of the muscles and nerves. Learn about why this kind of testing is done.

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    What is an EMG?

    EMG stands for electromyogram. This test measures the electrical activity of the muscles when they are working to contract and when they are at rest. EMG testing is used to diagnose conditions that cause muscle tissue damage or damage to the junctions between the muscles and nerves. Conditions that can cause these problems include Lou Gehrig's disease, myasthesnia gravis, and herniated disc. The EMG test can also be used to find the reason for muscle weakness or twitching. Any condition that affects the muscles, spinal cord, or nerves supplying muscles can cause these symptoms.

    During an EMG, small solid needles are inserted into the muscles in order to measure electrical activity. While this sounds painful or uncomfortable, the pain is much less than that experienced with injections since no liquid is being injected into the body. The technician will instruct you to contract your muscles by performing specific movements during the test.

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    What is a nerve conduction study?

    Nerve conduction studies differ from the electromyogram because they measure how well the nerves function. This includes measuring how fast electrical signals can be transmitted by the nerves. This type of study is often used to help diagnose conditions such as Lou Gehrig's disease, Guillain-Barre syndrome, carpal tunnel syndrome, and peripheral neuropathies.

    During a nerve conduction study, you will work with a technician who has been trained in administering such a test. Small electrodes will be taped to your skin and you may experience an unpleasant tingling or electrical shock. The technician will use these electrodes to measure how well and how quickly nerve impulses are transmitted.

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    You should inform your doctor about any medications that you are taking. Some medications can affect the transmission of nerve impulses or how well the muscles function, making it difficult to get accurate test results. If you take blood thinners, your doctor will ask you to stop taking them before the test so the results are more accurate. If you have a pacemaker, you should tell your doctor before having an EMG nerve test.

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    WebMD. "Electromyogram (EMG) and Nerve Conduction Studies." Accessed 29 June 2009.

    eMedicineHealth. "Electromyography." Accessed 29 June 2009.