Electromyography (EMG)

(EMG)

Definition

This test measures and records the electrical activity that muscles [2] generate at rest and in response to muscle [2] contraction.

EMG of the Shoulder

EMG shoulder 2

Parts of the Body Involved

Arms
Legs
Trunk
Back

Reasons for Procedure

Electromyography (EMG) is often done at the same time as nerve conduction studies [3], which help to diagnosis peripheral nerve disorders.

EMG is most often done to:

Aid in diagnosing the source of pain [4], cramping, or weakness in the muscles [2] and nerves
Differentiate between true muscle [2] weakness and limitations due to pain [4]
Determine if muscles [2] are working properly
Distinguish between muscle [2] and nerve disorders

Risk Factors for Complications During the Procedure

Hemophilia [5] and other bleeding disorders
Use of blood-thinning medications

What to Expect

Prior to Procedure

Your doctor will likely do the following:

Medical history
Review your medications
Physical exam
Neurological exam

In the days leading up to the test:

Avoid aspirin, aspirin-containing products, or anti-inflammatory drugs (eg, ibuprofen) for one week before the EMG
Ask your doctor if you need to stop taking any of your medications
If you have myasthenia gravis [6], ask if you should take any medication before the test
If directed to, avoid cigarettes, coffee, tea, and soft drinks for 2-3 hours before the test
Take a bath or shower before the test.
On the day before, do not use lotion or oil
Wear comfortable clothing, but expect to change into a hospital gown

Anesthesia

None

Description of the Procedure

The doctor inserts a small needle electrode into a muscle [2] at rest and moves the needle in the muscle [2]. Each movement of the needle and muscle [2] contraction produces a waveform. This waveform is recorded and analyzed. The test is repeated on different muscles [2] and limbs.

After Procedure

No special activities or procedures

How Long Will It Take?

30-90 minutes

Will It Hurt?

You may have pain [4] when the electrodes are inserted, which feels like an injection into the muscle [2]. After the test, you may have muscle [2] aches and discomfort for several days. Warm compresses and pain [4] medication may help.

Possible Complications:

Infection
Bleeding
Increased pain [4]

Average Hospital Stay

None

Postoperative Care

Resume any medication you stopped before the test
Resume normal activities as tolerated

Outcome

The doctor doing the EMG may discuss the results with you. Also, a report will be sent to your regular doctor, who will recommend treatment based on the tests, the exam, and your symptoms.

Call Your Doctor If Any of the Following Occurs

Signs of infection, including fever and chills
Redness, swelling, increasing pain [4], excessive bleeding, or discharge around the needle sites

RESOURCES:

National Institutes of Health
http://www.nih.gov/ [7]

National Institute of Neurological Disorders and Stroke
http://www.ninds.nih.gov/ [8]

CANADIAN RESOURCES:

BC Health Guide
http://www.bchealthguide.org/ [9]

Health Canada
http://www.hc-sc.gc.ca/index_e.html/ [10]

References:

Medical encyclopedia: electromyography. National Library of Medicine website. Available at: http://www.nlm.nih.gov/medlineplus [11]. Accessed August 1, 2003.

What to expect during your EMG test. American Association of Neuromuscular & Electrodiagnostic Medicine website. Available at: http://www.aanem.org/index.cfm? [12]. Updated March 2005. Accessed June 5, 2008.

Young RR, Hutton JT, Homan RV. Gait and movement disorders. American Academy of Neurology website. Available at: http://www.aan.com/familypractice/html/chp8.htm [13]. Accessed June 5, 2008.

Last reviewed November 2007 by Judy Chang, MD, FAASM [14]

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical [15] advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health [16] provider prior to starting any new treatment or with any questions you may have regarding a medical [15] condition.