Electrodiagnostic Medicine Nerve Test

EMG Test for Carpal Tunnel Nerve Pain

What is Electrodiagnostic Medicine?

The electrodiagnostic medicine consultation is a direct extension of the neurologic portion of the physical examination.

The examination can be helpful in evaluating the causes of numbness, tingling, discomfort, weakness, fatigue, and muscle cramping. Several types of tests are used to study nerve and muscle function. These include nerve conduction studies (NCSs), needle electromyography (EMG), and evoked potentials.  Just as an MRI takes a picture of your anatomy, an EMG demonstrates the physiology or how your nerves and muscles are working or not properly working.

An electrodiagnostic medicine consultant undergoes special training in electrodiagnostic medicine procedures. The knowledge and expertise gained from such specialized medical training maximizes the ability of the consultant to consider appropriate differential diagnoses in planning and performing the electrodiagnostic examination. The expertise enables the consultant to assist referring physicians in establishing diagnoses, determining prognoses, and assisting in proper management. The examination usually takes 20 to 60 minutes. There are no restrictions on activity before or after the testing and there are no lasting aftereffects.

NCS and evoked potentials should be performed by a physician or a trained technologist under the direct supervision of a physician. The needle EMG examination should be performed by a physician only with special training in this area.  Dr. O’Leary performs all phases of the test and does not utilize a tech or assistant for any part.

Nerve Conduction Studies

NCS test how well signals travel along a nerve and can help find the cause of abnormal nerve function. Signals are made to travel along the nerve by applying small electric pulses to the nerve at one site and recording the response at a different place along the nerve. The small electric pulses cause a short, mild tingling feeling. The nerve’s response is picked up by a recording instrument and then is measured by the physician or technologist performing the test. Several nerves may need to be tested depending on the type of problem.

Needle Examination (EMG or Electromyogram)

During the needle EMG portion of the examination, the physician inserts a small needle into a muscle to record the electrical activity of the muscle. The electrical activity of the muscle is fed into the recording instrument and the physician then analyzes it by looking at a signal on the scope and listening to the sounds the activity makes through the speaker. This test can help determine if there are abnormalities in the muscle or the nerve going to it.

There may be mild discomfort when the needle is inserted into the muscle. The needles are discarded after use or sterilized before being used on another patient to prevent the transmission of infections.

Special Precautions

You should inform the physician prior to the examination if you are on blood thinners or have hemophilia. The physician should also be informed if you have a cardiac pacemaker or use a transcutaneous electrical nerve stimulator (TENS) unit. Avoid using skin lotions the day of the test. If you have myasthenia gravis you should ask your physician whether or not to take medications, such as Mestinon, before the examination.


When the examination is completed, the electrodiagnostic medicine consultant will analyze the results and report them to the physician who referred you for the tests. Your referring physician will use the test results to help decide on proper management.

Patient Questions

Dr. O’Leary has personally performed over three thousand electrodiagnostic tests and never has a patient asked to stop due to it being unpleasant or otherwise.  If you have questions, they will be answered at the time of your examination.