Electromyography refers to a specific category of electrodiagnostic testing that is used to analyze the activity of the peripheral nervous system, specifically, the electrical activity within muscle tissue, for the purpose of collecting information, assessing neurological injury, and diagnosing a wide range of conditions.
If you or someone you know has an EMG test coming up, hopefully, the following questions and answers will be helpful.
What Is an EMG?
An electromyography test, more commonly known as an EMG test, is an electrical test administered to record the electrical activity in muscle tissue.
An EMG test may consist of two parts; nerve conduction testing (also known as a nerve conduction study or NCS) and possibly also an intramuscular (needle) exam. The nerve condition study tests the electrical response of the body’s nerves to an electrical stimulus. The needle EMG is used to “listen” to and record the electrical signals in the muscle’s tissues.
Electromyography (EMG) tests are often performed to check for Wallerian degeneration (a specific type of nerve damage) that can result from injury, muscular dystrophy, polymyositis, and myasthenia gravis, as well as to test for local conditions, such as carpal tunnel syndrome,
How Is an EMG Recorded?
There are two basic ways in which an EMG is recorded. One method is with a surface electrode, typically made of silver or silver chloride. Surface electrodes of silver or silver/chloride offer suitable signal quality and signal-to-noise ratios and are very stable; this method is also non-invasive and does not require anesthetization.
Intramuscular EMG recordings are taken via EMG needles, which are very thin-wire electrodes that must be inserted into the muscle of interest. Intramuscular recordings taken with EMG needles also offer additional benefits, such as secure electrode contact and the ability to record signals from deep within muscles with little crosstalk.
What Preparation Is Necessary for the Test?
Speak to your healthcare provider about any preparations you will need to make before an EMG, extremely important and practically the only contraindication are the use of anticoagulants, before the test, due to an increase risk of bleeding .
However, as a general rule, you should make sure your skin is clean (don’t use any creams or skincare treatments) and wear loose, comfortable clothing that will allow easy access to the test area.
How Long Does the Test Take?
An EMG should take anywhere from an hour to an hour and a half, although it could take as long as two hours.
Does It Hurt?
While EMG needles are used in electromyography, they are very small and fine. Some patients report a little pain or cramping or a little muscle soreness in the days following a needle electrode EMG test.
For a nerve conduction study, some patients report feeling a mild shock, similar to static.
What If an EMG Registers Abnormal Electrical Activity?
Abnormal results recorded during an EMG test can indicate a wide range of conditions affecting the nerves and muscles, including but not limited to:
- Alcoholic Neuropathy
- Muscular Dystrophy
- Wallerian Degeneration
- Carpal or Cubital Tunnel Syndrome (affecting the wrists or elbows)
- Muscular Denervation
- Guillain-Barré Syndrome
- Sciatic Nerve Dysfunction
- And a wide range of myopathies
EMG tests are also used to diagnose a wide range of other conditions affecting the nerves and muscles. Speak with your physician regarding these if you have additional questions.