Many individuals may experience muscular aching and nerve pain, unexplained weakness in the arms and legs, and/or numbness and tingling in one or more areas of the body. These symptoms may be the result of diseased or injured nerves or muscles. Some common conditions which may cause these symptoms are carpal tunnel syndrome, pinched nerves in the neck or back or peripheral neuropathy, just to name a few. Typically, a good history and physical exam by your health care provider can help provide answers. However, in cases where the cause is unclear or the severity of the potential location needs clarification, electrodiagnostic testing can add valuable information.
Electrodiagnostic testing is an important method for physicians to distinguish between many nerve and muscle disorders. The purpose of which is to help figure out whether there is a problem in the nervous system and if so, where the problem is occurring and the severity. The term electrodiagnostic testing encompasses many different tests, the most common of which are nerve conduction studies (NCS) and electromyography (EMG). Oftentimes, both NCS and EMG are referred to as just EMG. This is because these two tests are nearly always done together. It is important that these tests be viewed as an extension of a thorough neurological and musculoskeletal examination and the results be interpreted in the context of the patient’s clinical presentation. For this reason, an NCS and EMG should be performed by a qualified physician trained in this subspecialty.
EMG and nerve conduction testing assesses the function of the peripheral nervous system (the nerves of the body once they leave the spine). While this test does not test for pain or detect pain, it is useful for determining if there is an underlying neuropathic condition that may be causing pain or the symptoms.
The nerve conduction study is most often done first. In this part of the test, several electrodes are attached to the surface of the skin over a specific muscle or sensory nerve distribution. The nerves are then stimulated through electrical impulses and the responses recorded over the muscle or sensory nerve ending. Information can then be gathered about the function of the nerves. It can be determined how fast or how slow the nerve is conducting impulses, how much information the nerve is carrying and whether or not there is blockage of the impulse at certain sites. This can give valuable information about nerve function and what components of the nerve may be affected. It can also give information on the severity or prognosis of a nerve injury.
The second part of the test, electromyography, assesses muscle function. A very fine needle, about the size of a small acupuncture needle, is inserted into a muscle. No electrical stimulation is performed. The muscle is then assessed at rest (relaxed) and during contraction. In severe nerve injuries or in certain muscle diseases, abnormal electrical activity can be seen when the muscle is at rest. When the muscle is contracted, groupings of muscle fibers are seen as wave forms on the computer screen. Information can be gained about muscle function, such as whether there has been remote or chronic nerve injury that has healed, ongoing nerve injury or other muscle disorders.
An EMG test is a very low-risk procedure. It can be for performed in individuals with pacemakers, with appropriate precautions. Some patients report feeling some aching or soreness in the area that has been tested. The soreness is usually of short duration and typically can be relieved with over-the-counter pain medications such as ibuprofen or Tylenol. Occasionally there may be bruising or swelling at the needle insertion sites. FBN
By John Ledington, M.D.
John Ledington, M.D., is a physiatrist at Northern Arizona Orthopaedics and practices in the Spine and Pain Center. He specializes in the non-surgical conservative treatment of spinal pain. Dr. Ledington is board certified in Physical Medicine and Rehabilitation and has a sub-specialty board certification in Pain Medicine and Electrodiagnostic Medicine.
