What is an EMG?

EMG stands for electromyogram which loosely translates electrical testing of muscles but in fact has come to mean electrical testing of nerves and muscles.

Who performs the EMG?

The EMG is performed by a specialist.  The Electromyography, who is usually a Neurologist or a Physiatrist.  A Physiatrist is rehabilitation specialist.  Parts of the test may be performed by a specially trained technician.  This procedure is an in-office procedure and does not require any hospitalization.

For what problems are EMG's ordered?

An EMG is ordered when a patient is having problems with their nerves or muscles.  Testing will be done to the nerves and muscles of the body extremities, looking for a problem in either one of these areas.  An EMG may be ordered to see if you have a pinched nerve in your back or neck.  If you have tingling, numbness, or radiating pain to you arms or legs, an EMG may show if you have a nerve entrapment somewhere or a nerve injury such as the carpal tunnel syndrome.  Weakness of the muscles may be indicative of nerve or muscle disease and may require an EMG.  there are numerous other reasons that may suggest the need for an EMG.  If you have any questions ask your doctor.

What happens during an EMG/NCV?

The test consists of two parts, all though one may be done without the other.  You will be lying down on an exam table.

In the first part Nerve Conduction Velocity Study.  In this part brief electrical impulses are delivered to your arm or leg in an effort to determine how fast or slow your nerves are conducting the electrical current and therefore in what state of health or disease they may be.  The doctor will attach small 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 at this time you will feel a tingling sensation that may or may not be painful.  Between the brief shocks you will not feel pain.  Due to the fact that there are several nerves in each extremity which need to be tested, the procedure is repeated until each nerve has been tested per extremity.  The amount of current applied is always kept at a safe level.  Patients who have a pacemaker or other electrical devices should not worry since the currently will rarely interfere with these devices.  The doctor or technician performing the study will occasionally be pausing to make calculations and measurements.

The second part of the test is the Needle Examination and as the name suggests needles will be used.  The needles that are used are very fine (thin) and about one and a quarter inches long and are disposable which means they are only used once and discarded  after each patient.  This part of the test checks muscles to see if there has been any damage to the muscle as a result of nerve damage or if the disease involves the muscle itself.  Usually 5 to 6 muscles are tested per extremity.  If you have problems in more than one area, additional muscles may need to be studied.  The needle is inserted into 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 like radio static.  The painful part of this section is when the needle is first inserted through the skin and when the needle is repositioned inside the muscle.  Once inside the muscle the sensation is usually uncomfortable or feels like pressure rather than pain.  During the needle exam no electrical shocks are delivered and since the needle probe is used only as recording device no injections are given through the needle into the muscle.  On average a muscle is sampled for 2 to 5 minutes thought his may vary depending on the problem being investigated.

How long does an EMG take?

The nerve conduction part of the test usually takes longer than the needle exam because the doctor or technician needs to make calculations and measurements during it.  If one extremity is studied on average it takes between 15 and 30 minutes.  The needle exam for one extremity takes between 15 and 10 minutes.  You should plan on being in the examination room for an hour if one extremity is being studied and longer if more extremities need to be tested.

How should I prepare for an EMG?

There is really no preparation needed.  You should shower the night before to remove natural oils that may interfere with the application of the electrodes.  You should also avoid lotion because it may interfere with the needle portion of the test.  You do not need to fast, or eat any particular types of foods before the test.  You can drive yourself to and from the test your self so you will not need to bring anyone to drive you.  You can resume your normal activities after the test.  If you are having you upper extremities studied (neck and arms) you should wear a t-shirt so you can avoid wearing a gown.  If you are having lower extremities studied (lower back and legs) you should wear gym shorts or sweat pants that can pushed above your knees.  Try to avoid wearing blue jeans and tight fitting long sleeved shirts or you will have to wear a gown during the test.

The doctor performing the test has a general idea of what the findings are during the test.  The full results are only arrived at after more calculations and measurements are performed after the test.  The results therefore are usually not ready until later that day or even the next day in more complex cases.