What happens during an EMG?
During this test, you will be lying on an examination table, next to an EMG machine (which looks like a desktop or laptop computer). The test consists of two parts, though at times one may be done without the other. The first part is called Nerve Conduction Studies. In this part some brief electrical shocks are delivered to your arm or leg in an effort to determine how fast or slowly your nerves are conducting the electrical current and therefore in what state of health or disease they may be. You see, a nerve works something like an electrical wire. If you want to see if the wire is functioning properly, the easiest thing to do is to run electricity through it. If there are any problems along its length, you will know it by a failure of the current to go through. To do this, the doctor will attach small recording electrodes to the surface of one part of your limb, and will touch your skin at another point with a pair of electrodes delivering the shock. When this happens, you will feel a tingling sensation that may or may not be painful. Between the brief shocks you will not feel pain. As there are several nerves in each extremity which need to be tested, the procedure is repeated 3 or 4 times or more per extremity studied. The amount of current delivered is always kept at a safe level. Patients wearing pacemakers or other electrical devices need not worry since this current will rarely interfere with such devices. During the nerve conduction study, the doctor or the technician performing the study will occasionally be pausing to make calculations and measurements.
The second part of the test is called Needle Examination and as the name implies, involves some needle sticking. The needles used are thin, fine and about one and a quarter inches long. This part tests the muscle to see if there has been any damage to it as a result of the nerve problem or if the disease involves the muscle itself rather than the nerve. Usually 5 to 6 muscles are sampled in one extremity, but occasionally, if you have problems in more than one area, additional muscles may need to be studied. The needle is usually inserted in the relaxed muscle and moved inside gently in order to record the muscle activity. When this is done, you will be able to hear the sound of the muscle activity amplified by the EMG machine; it will sound something like radio static. The painful part of this section is when the needle is first inserted through the skin since all of the pain receptors are located in this area. Once inside the muscle, the sensation is usually perceived as discomfort or pressure rather than pain. During the needle exam, no electrical shocks are delivered. Also, since the needle probe is used here only as a recording device, no injections are given through the needle into the muscle. On the average, a muscle can be sampled in 2 to 5 minutes though this may vary with the type of problem being investigated.
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