Electrodiagnosis: EMG/NCS

What is an EMG?
An electrodiagnostic study is often referred to as an 'EMG'. This study is usually composed of two parts; nerve conduction studies (NCS) and needle electromyography (EMG). This study is usually ordered to determine if there is a problem with your muscles, nerves, or the connection between the two. Patients are usually referred for an electrodiagnostic study because they have numbness, tingling, or weakness. This test is very important because it can help determine where the problem is, how long it has been going on for, and can help predict the prognosis for recovery.

Dr. Weitzenberg routinely conducts a focused history and physical examination before every electrodiagnostic study. This helps him to focus on the specific problem and determine what specific components of the exam will best help find an answer. Dr. Weitzenberg recieved 3 years of specific training to conduct these studies while attending his residency program at the University of California Davis Medical Center in Sacramento, California.

Nerve Conduction Studies (NCS)
Nerve conduction studies show how the body’s electrical signals are traveling through a nerve. This is done by applying small electrical shocks to the nerve and recording the responses in the nerve or muscle at a distant location. These shocks cause a quick, mild, tingling feeling. Several nerves are usually tested at several different locations. The recorded responses tell us how much time it took to travel a set distance, how fast it is traveling, how large it is and if there is any slowing at a particular location. Both motor and sensory nerves are routinely tested.

Needle Electromyography (EMG)
For this part of the exam, a small, thin needle is inserted into several muscles to see if there are any abnormalities in the muscle, the connection between the muscle and nerve or in the nerve itself. A new needle is used for each patient, and it is thrown away after the test. There may be a small amount of pain when the needle is inserted into the muscle. Only the muscles necessary to decide what is wrong are tested. The doctor will look at and listen to the electrical signals that travel from the needle to the EMG computer. The muscles give off electrical signals similar to the way an electrocardiogram (ECG) detects the electrical signals of the heart muscle (myocardium). If there is an abnormality, the electrical signals will be altered, which will change the sound and shape of the responses displayed by the computer. The doctor then interprets these signals.

How Long Will These Tests Take?
The tests usually take 20 to 90 minutes. You can do any of your normal activities, like eating, driving, and exercising, before the tests. You also can do your normal activities after the tests. There are no lasting side effects from the tests.

How Should I Prepare For the Tests?
Please notify Dr. Weitzenberg if you are taking aspirin, blood thinners (like Coumadin), have a pacemaker, or have hemophilia. Take a bath or shower to remove oil from your skin. Do not use body lotion on the day of the test. If you have Myasthenia Gravis, ask your EMG doctor if you should take any medications before the test.

When Will I Know the Test Results?
Dr. Weitzenberg will discuss your test results with you and send a complete report to your primary doctor. After the exam, check with your primary doctor who sent you for the electrodiagnostic study for the next step in your care.

Link(s):
teleemg.com A great website all about EMG and Nerve Conduction Studies!
AAEM The American Academy of Electrodiagnostic Medicine website.
ABEM The American Board of Electrodiagnostic Medicine website.

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