by Jeffrey R. Carlson, MD
Electromyography (EMG) is a diagnostic procedure that is used to the reveal health or dysfunction that exists in nerves, muscles or in how the two communicate with each other. The motor neurons are the specialized nerve cells that transmit information from the brain to the muscles. Because these motor neurons use electrical signals to communicate with the muscles, the speed and strength of these signals can be measured and interpreted to reveal disease, dysfunction or the need for further investigation.
The procedure is often ordered when a patient has neurologic symptoms such as numbness, tingling or burning, limb pain, muscle cramping or weakness. The EMG is helpful in that it can confirm or rule out conditions such as muscular dystrophy, myasthenia gravis, polio and amyotrophic lateral sclerosis, where the nerves have difficulty communicating with muscles. An EMG will not show brain or spinal cord disease.
At OSC, we commonly use EMG to diagnose disorders such as carpal tunnel syndrome, peripheral neuropathies or herniated discs in the spine, where nerves are being compromised by disease, a structural problem or inflammation.
The EMG consists of two parts – one being a sterile, one-use needle EMG and one being a nerve conduction study. You may have one or both as ordered by your doctor. The needle EMG involves the insertion of a needle electrode into the affected muscle to record its electrical impulses. A nerve conduction study involves taping electrodes (no needles) to the skin to measure how electrical signals travel between two or more points.
If your physician requests an EMG, you will need to inform them if you have the following:
- hemophilia, a blood-clotting disorder
- a pacemaker or deep brain stimulator
- you take blood thinners, such as Coumadin, Warfarin or aspirin (you may have to discontinue these a few days before the exam)
Before your exam, you should bathe or shower to remove any oils from the body. You will need to refrain from applying lotion, cream or oil to your skin before having the test.
When you report to our office for your appointment, you will be taken to the EMG room and asked to change into a gown. The skin in the testing area will be cleaned to provide a clear surface for the test. Dr. Andrus will begin the testing based on what area of your body is symptomatic and where the suspected nerve or muscle dysfunction is located.
Electrodes, either needle or skin surface, will be inserted or applied. The needle insertion may be mildly uncomfortable, but any discomfort should cease as soon as the needle is removed. Dr. Andrus will measure the electrical activity of your nerves and muscles at rest and then during activity, which will require you to flex, extend or release and contract your muscles. You may also be asked to change positions during the test. A very mild current will be applied to the electrodes so that Dr. Andrus can artificially stimulate muscle activity to see how your muscles and nerves respond. This will cause a twitch or a small spasm of the muscle. If you find having a needle EMG uncomfortable, you can ask for a moment to rest during the procedure.
The test takes about 30-60 minutes, depending on the areas to be tested. Dr. Andrus may be able to share some of the results from the test while you are in the office; however a full report may take several days. Your test results will be used to determine what treatment may be necessary.
There are really no risks for a nerve conduction study as the electrical stimulus used is not strong enough to damage tissue.
There are very few risks to having a needle EMG. Though the rate for complication is very small, they include infection, bleeding and nerve injury at the needle insertion site. You may experience minor bruising at the site where the needle(s) was inserted, feel mild pain or muscle soreness. You can take an over-the-counter anti-inflammatory such as Aleve for any residual muscle pain. Icing the area may also minimize bruising, if you are prone to do so.