Electromyography (EMG)

Electromyography (EMG) is a diagnostic test that helps detect neuromuscular abnormalities by measuring electrical activity in the muscles.

How is an EMG performed?

A very thin needle (electrode) will be inserted through the skin and into the muscle. Once the electrode is in place, the patient will be asked to either contract their muscles or keep their muscles relaxed. The electrode will detect electrical activity and results will be displayed on a nearby monitor (oscilloscope).

A nerve conduction velocity (NCV) test is often performed at the same time as an EMG. An NCV helps to differentiate a nerve disorder from a muscle disorder.

How do you prepare for an EMG?

Typically, not a lot of preparation is necessary for an EMG.

• Avoid using any creams or lotions on the day of the test.
• Fasting is usually not required, but, in some cases, patients will be asked to refrain from smoking cigarettes or drinking caffeinated beverages for up to two to three hours before the test.
• Notify your physician if you have a pacemaker.
• Tell your physician about all the medications and herbal supplements you are taking.
• Dress in clothing that enables easy access to the area to be tested.

What conditions are diagnosed by using electromyography?

An EMG can be used to diagnose a wide variety of neuromuscular diseases, motor problems, nerve injuries, or degenerative conditions, such as:

• Amyotrophic lateral sclerosis (ALS)
• Carpal tunnel syndrome
• Cervical spondylosis
• Guillain-Barre syndrome
• Lambert-Eaton syndrome
• Muscular dystrophy
• Myasthenia gravis
• Peripheral neuropathy
• Polymyositis
• Radial nerve dysfunction
• Sciatica nerve dysfunction

Contact us about electromyography

For patients who would like to learn more about electromyography, or for physicians who would like to schedule a test for a patient, please contact the Brigham and Women’s Hospital Neuromuscular Service at (617) 732-8046.