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Electromyogram (EMG) and Nerve Conduction Studies

An electromyogram (EMG) measures the electrical activity of muscles at rest and during contraction. Nerve conduction studies measure how well and how fast the nerves can send electrical signals.

Nerves control the muscles in the body with electrical signals called impulses. These impulses make the muscles react in specific ways. Nerve and muscle problems cause the muscles to react in abnormal ways.

If you have leg pain or numbness, you may have these tests to find out how much your nerves are being affected. These tests check how well your spinal nerves and the nerves in your arms and legs are working.

Why It Is Done

An EMG is done to:

  • Find diseases that damage muscle tissue, nerves, or the junctions between nerve and muscle. These problems may include a herniated disc, amyotrophic lateral sclerosis (ALS), or myasthenia gravis (MG).
  • Find the cause of weakness, paralysis, or muscle twitching. Problems in a muscle, the nerves supplying a muscle, the spinal cord, or the area of the brain that controls a muscle can cause these symptoms. The EMG does not show brain or spinal cord diseases.

A nerve conduction study is done to:

  • Find damage to the peripheral nervous system, which includes all the nerves that lead away from the brain and spinal cord and the smaller nerves that branch out from those nerves. This test is often used to help find nerve problems such as carpal tunnel syndrome or Guillain-Barré syndrome.

How To Prepare

Tell your doctors all the medicines, vitamins, supplements, and herbal remedies you take.

  • Some medicines can affect the test results. You may need to stop taking some medicines before you have this test.
  • If you take blood thinners, such as warfarin (Coumadin), clopidogrel (Plavix), or aspirin, your doctor will tell you if you should stop taking these medicines before your procedure. Make sure that you understand exactly what your doctor wants you to do.

Wear loose-fitting clothing so your muscles and nerves can be tested. You may be given a hospital gown to wear.

Since the electrodes are attached to your skin, make sure it is clean and free of sprays, oils, creams, and lotions.

You may be asked to sign a consent form that says you understand the risks of the test and agree to have it done.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done

An EMG is done in a hospital, clinic, or doctor's office. It may be done in a room that stops any outside electrical interference. The test may be done by an EMG technologist or a doctor.

WebMD Medical Reference from Healthwise

Last Updated: March 12, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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