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APM Spine & Sports Physicians

Electromyography and Nerve Conduction Study

Electromyography/Nerve Conduction Study (EMG/NCS) is a two-part test to diagnose disease of the nerves and muscles.

This test evaluates peripheral nerves. These nerves run outside the central nervous system (brain and spinal cord) and provide stimulation to the face, torso, skin, extremities, blood vessels, and internal organs. They are not protected by bone and are susceptible to injury and toxins.

Peripheral nerves have long extensions called axons that carry electrical signals. Muscles are stimulated by nerve cells called motor neurons. These motor neurons cause electrical activity in the muscle, which then causes a contraction or tightening of the muscle.

An Electromyography (EMG) is done to find diseases that damage muscle tissue and nerves or the function between nerve and muscle. An EMG measures the electrical activity in muscles. At rest, there should not be any activity, and with varied stimulation to the muscle, the activity level will change. Measuring this activity can help to differentiate problems in a muscle, nerves supplying a muscle, the spinal cord or the brain, which can cause paralysis, weakness or muscle twitching.

Nerve Conduction Studies (NCS) are performed to find damage or injury to the peripheral nervous system. The peripheral nervous system includes all nerves that lead away from the brain and spinal cord and the smaller nerves that branch out from those nerves. An NCS measures the ability of specific nerves to transmit electrical impulses. NCS are used to help in the diagnosis of such conditions as nerve entrapments, plexopathy, peripheral neuropathy and radiculopathy.

Why do I need to have these tests?

Measuring the electrical activity in nerves and muscles helps to detect the presence, location and extent of nerve and muscle disorders. EMG is often used to evaluate unexplained muscle weakness, twitching or paralysis and to find the causes of numbness, tingling and pain. It can help differentiate between true weakness and reduced use because of pain or lack of motivation. EMG can also determine whether a muscle disorder begins in the muscle itself or is caused by a nerve disorder.

How should I prepare for an EMG/NCS?

On the day of your examination do not apply any creams, oils, moisturizers, perfume or powders to your skin. Wear comfortable clothing. Please inform your physician if you are taking Coumadin® or have a pacemaker/defibrillator.

What can I expect on the day of the test?

Nerve conduction studies (NCS) electrodes will be applied to your skin. An electrical stimulus is placed directly over the nerve to be studied, and a recording electrode is placed over the muscle supplied by the nerve. Brief repeated stimuli are administered to the nerve, and the nerve’s response is measured. You will feel a tingling sensation and twitching in your muscle.

The electromyogram (EMG) section includes a small sterilized needle being inserted in the muscles to be tested. There is some discomfort with the needle insertion, but most people tolerate this without difficulty. The discomfort you will experience is less painful than getting a shot or having blood drawn. You will be asked to relax and contract the muscles that are being examined. The electrical activity of the muscle will be measured and displayed as electrical waves on a screen.

You may notice some bruising after the needle portion (EMG). Ice to the sore areas can help with the discomfort and limit the bruising. Any time the skin is penetrated with a needle, there is a risk of infection, although its occurrence is very rare.

When will the test results be available?

Your report will be typed at the completion of your test and faxed to your physician within 24 hours.