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What is electromyography?

Electromyography (ee-lek-troh-meye-OG-rah-fee) is a test that is also called an electromyogram (ee-lek-troh-MEYE-oh-gram) or EMG. It measures electrical activity of the muscles at rest and when they are used. It also tests the electrical activity of the nerves that control muscles. During your EMG, caregivers may also do a nerve conduction study (NCS). This test measures how fast the nerves send impulses to the muscles (messages telling the muscles to move). EMG and NCS may be part of a group of tests called an electrodiagnostic (ee-lek-troh-deye-ag-NOS-tik) exam.

Why do I need an EMG?

An EMG is used to test how well your muscles and nerves are working. It may be used to help caregivers learn if you have a muscle and nerve problem or disease. An EMG and NCS can help caregivers learn about weakness and problems with feeling such as tingling, numbness or pain. These tests can help caregivers learn about uncontrolled muscle movements such as twitches, tremors or spasms (jerking). Your caregivers may use EMG and other test results to help diagnose and plan treatment for your health problem.

What should I do to get ready for an EMG?

  • Some medicines should not be taken before having an EMG. These may include muscle relaxants or medicines that help control or decrease spasms (jerking), tremors (shaking) or muscle stiffness. Take a list of your medicines or the medicine bottles to your caregiver. Ask your caregiver if any of your medicines should not be taken before your EMG. Do not stop taking any medicines without asking your caregiver first.
  • Avoid smoking or having caffeinated food and drinks three hours before the EMG. Caffeine may be found in coffee, tea, soda pop, and sports drinks and foods. Read the ingredient label if you think a food or drink may have caffeine in it. Caffeine may change the result of your EMG.
  • Tell your caregiver if you have a cardiac pacemaker or stimulator. Tell your caregiver if you are taking an anticoagulant (blood thinner) medicine or have a bleeding disease.
  • Eat your regular breakfast or lunch before the EMG.
  • Take a bath or shower on the day of your EMG. Do not rub lotion, oil or cream onto your skin.
  • Wear loose-fitting, comfortable clothing to your EMG.

Informed consent

is a legal document that explains the tests, treatments, or procedures that you may need. Informed consent means you understand what will be done and can make decisions about what you want. You give your permission when you sign the consent form. You can have someone sign this form for you if you are not able to sign it. You have the right to understand your medical care in words you know. Before you sign the consent form, understand the risks and benefits of what will be done. Make sure all your questions are answered.

How is an EMG performed?

  • You may put on a hospital gown or wear your clothing if it is loose-fitting. You will sit or lie down in a position that puts the muscles to be tested at rest. Caregivers will clean your skin with alcohol or antiseptic (prevents germs) soap. Thin needles will be put into the muscle to be tested. You may feel some pain as the needles are put through your skin and into your muscle. You may feel a dull ache while the needles are in your muscle. If you are also having nerve conduction studies (NCS), patches will be taped to your skin. Both needles and patches have wires on them that will be connected to a machine.
  • Caregivers will test your muscle while it is resting (not moving). Then you may be asked to contract (tighten) your muscle, for example by bending your arm. Caregivers may take the needles out of one muscle and place them in other muscles. You may see a recording of your muscle movements on a computer or TV-like screen. You may also be able to hear the recording from a speaker. During the NCS, the pads on your skin will deliver a very mild (weak) shock to your muscle. The shock will only affect the muscle being tested and does not go to the rest of your body. It may feel like tingling or slight numbness, or may cause your muscle to twitch.

What should I do after an EMG?

You may do the following if your muscles feel sore or bruised after the EMG:

  • Apply warm compresses to the sore areas where the needles were placed. To make a warm compress, dip a clean washcloth in warm water. Wring out the extra water and put it on your sore muscles for 15 to 20 minutes, three to four times each day.
  • Your caregiver may tell you to take nonsteroidal anti-inflammatory medicine (NSAIDs) after your EMG. This medicine may help decrease inflammation (in-flah-MAY-shun) (redness and swelling) and soreness caused by the EMG needles. This medicine can be bought with or without a doctor's prescription. This medicine can cause stomach bleeding or kidney problems in certain people. Read the label warnings, and follow dosage directions carefully.

Call your caregiver if:

  • You cannot be there at the time your test is to be done.
  • The problem for which you are having the test has gotten worse.
  • You have a fever.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your caregivers to decide what care you want to receive. You always have the right to refuse treatment.

© 2013 Truven Health Analytics Inc. Information is for End User's use only and may not be sold, redistributed or otherwise used for commercial purposes. All illustrations and images included in CareNotes® are the copyrighted property of the Blausen Databases or Truven Health Analytics.

The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.