Electromyography (EMG)

The measurement and recording of electrical activity generated in muscle for diagnostic purposes. Active muscles produce an electrical current.

Parts of the Body Involved

Arms, legs, trunk, or back

Reasons for Procedure

Electromyography (EMG) is often performed at the same time as nerve conduction studies, which aid in the diagnosis of peripheral nerve disorders.

EMG is most often done for the following reasons:
  • To diagnose the source of pain, cramping, or weakness in the muscles and nerves
  • To differentiate between true muscle weakness and limitations due to pain
  • To determine if muscles are working properly
  • To differentiate between muscular conditions and dysfunction due to nerve disorders

Risk Factors for Complications during the Procedure

  • Hemophilia and other bleeding disorders
  • Use of blood-thinning medications

What to Expect

Prior to Procedure

Your doctor will likely do the following:
  • Physical exam
  • Neurological exam
  • Medical history
  • Review of medications
In the days leading up to your procedure:
  • Do not take aspirin, aspirin-containing products, or anti-inflammatory drugs (e.g., ibuprofen) for one week before the procedure
  • Check with your doctor about which of your other regular medications you should stop taking until after the tes
  • If you have myasthenia gravis, ask if you should take any medication before the test
  • Your doctor may request that you refrain from smoking or drinking coffee, tea, or soft drinks for two to three hours before testing
  • Take a bath or shower before the test
  • Do not apply any lotion or oil to your body on the day of the exam
  • Wear comfortable clothing, but expect to change into a hospital gown, if needed, to provide access to the muscles being tested
During Procedure - You lie on an exam table in a hospital gown

Anesthesia - None

Description of the Procedure - The doctor inserts small needle electrodes into a muscle at rest and applies a mild electrical current to stimulate the nerve. Several needles are needed to evaluate large, skeletal muscles. Each current produces a sound and movement, which are recorded on the machine and analyzed by the doctor performing the exam. The doctor asks you to contract the muscle, then watches and listens to the response. The process is repeated in different muscles. Both extremities may be tested for comparison.

After Procedure - No special activities or procedures

How Long Will It Take? 30-60 minutes

Will It Hurt? Patients report pain during the insertion of electrodes, which feels like a small intramuscular injection. The electrical stimulation is painful, and the aching and muscular discomfort may persist for several days. Warm compresses and a mild pain medication may help to relieve this discomfort.

Possible Complications:
  • Infection
  • Bleeding
  • Increased pain
Average Hospital Stay - None

Postoperative Care:
  • Resume any medication you stopped before the test
  • Resume normal activities as tolerated

Outcome

The doctor performing the EMG may discuss the results with you. Also, a report describing the outcome of the test will be sent to your regular doctor, who will make recommendations for treatment based on the results of all diagnostic testing, a clinical examination, and the history of your symptoms.

Call Your Doctor If Any of the Following Occurs

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