Electrodiagnostic Testing - Electromyography (EMG) - Rehabilitation Institute of Chicago

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Electrodiagnostic Testing (EMG/NCS)

The electrodiagnostic examination, electromyography, can be helpful in evaluating the cause of pain, numbness, tingling, weakness, fatigue and muscle cramping. X-rays and MRIs show the anatomy of bones and soft tissues. Electrodiagnostic tests look at nerve and muscle function to see if a nerve is “pinched” or not functioning well.

The testing can help your doctor establish the cause of your condition, determine prognosis, and properly manage your condition.

The doctors performing the testing will first examine your muscles and nerves by testing your strength and sensation in order to better plan the study. Then, after this  history and examination, the test is started and the test itself usually takes 1-2 hours to complete. How long it takes depends the problem you are having, including how many of your limbs are involved with your symptoms. For example, this test may require double this amount of time if you have symptoms in two or more limbs, or depending on the complexity of your condition. The testing generally includes what is known as nerve conduction studies (NCS) and needle electromyography (EMG).

What will I feel?

Nerve Conduction Studies (NCS)

With Nerve Conduction Studies, you will feel small shocks in the examined arm or leg. These shocks test how well signals travel along a nerve and can help find the cause of abnormal nerve function. The small electric pulses cause a short tingling/shock-type feeling with accompanied twitching of muscles. Several nerves may need to be tested depending on the type of problem, and sometimes testing is performed on the opposite limb to compare responses.

Needle Electromyography (EMG)

During the needle EMG portion of the examination, the physical medicine and rehabilitation specialist inserts a small needle into a muscle to listen to electrical activity of the muscle and evaluate the activity of your muscles on a computer. There is no shocking in this part of the exam. If there is something wrong with the muscle or nerve, abnormal sounds and signals can be detected. The muscles tested and the number of muscles evaluated depends on what kind of problem you are having.

Will this test hurt?

There is usually some discomfort when your nerves are stimulated during the Nerve Conduction Study and when the needle is inserted into the muscle during the EMG exam. Every person’s tolerance for discomfort is different, but the vast majority of people get through the test without difficulty and find the discomfort of the test tolerable. A new disposable sterile needle is used for each person so there is an extremely low risk of infection.

Are there any other risks?

A new disposable sterile needle is used for each person and we clean the skin with alcohol before needle insertion, so there is a very low risk of infection. This would be similar to the risk of infection when you get your blood drawn. There is also a risk of bruising particularly if you are on medications such as aspirin or other medications that affect how the blood clots.

Do I need to do anything special on the day of the test?

There are no restrictions on activity before or after the testing and there are no lasting aftereffects. You may take your regular medications including any pain medicines you may be taking. You will be awake for the entire test and communicating at all times with the physical medicine and rehabilitation specialist performing the test. We do not provide anesthesia or “knock you out” for the test – if we did, we would not get the information needed from your muscles and nerves.

You should inform the physician prior to the examination if you are on blood thinners (Coumadin or Warfarin) or if you have hemophilia. The physician should also be informed if you have a cardiac pacemaker, implanted defibrillator, or use a TENS unit (transcutaneous electrical nerve stimulator). Skin lotions affect the quality of the signals detected so please avoid using skin lotions the day of the test.

What about test results?

When the examination is complete, the physical medicine and rehabilitation specialist will analyze the results and report them to the physician who referred you for the test.

Your doctor’s office is usually called the same day with verbal preliminary findings and the final written report is sent to your doctor’s office within several days.

Your Questions

This information is not a substitute for an informed discussion between you and your doctor. If you have questions about electrodiagnostic testing, they can be answered at the time of your examination, or you can call the RIC's Electrodiagnostic Lab at 312-238-6098.