Electromyography or EMG is a diagnostic procedure that measures muscle response or electrical activity in response to nerve’s stimulation of the muscle. The EMG measures the electrical activity of the muscle at rest, during slight contraction, and during forceful contraction.
The EMG uses electrodes to transmit or detect electrical activity to help identify neuromuscular abnormalities. During the test, small, thin needles are placed in the muscle to record the electrical activity. When the needles are inserted, you may feel slight pain or discomfort. Your Ascendant physician will ask you to relax the muscle and to tense it slightly. The doctor will listen and watch a monitor that broadcasts the electrical signals. You will also be able to hear the signal sounds as you move the muscle.
The test usually takes 30-45 minutes. When the needles are removed, you may experience some soreness and bruising, but this will disappear in a few days. There are no long-term side effects.
The Nerve Conduction Study (NCS), another part of an EMG, involves electrodes taped onto the skin to measure the frequency, strength, and speed of conduction of an electrical pulse traveling between two or more points. NCS are typically performed at the same time as the EMG and can help predict nerve damage.
If you are taking blood-thinning medications, have an illness, or are at risk for infection, tell the doctor who is conducting the test. On the day of the test, do not put any lotions or creams on the area to be tested and do not wear any jewelry.
Your Ascendant physician may recommend electrodiagnostic testing for various conditions that can result from pressure on a nerve, particularly in the arm, elbow or wrist. These conditions are called “compressive neuropathies” and include:
- Carpal tunnel syndrome – pressure on the median nerve as it passes between the wrist bones and under the transverse ligament
- Thoracic outlet syndrome – pressure on the brachial plexus, a cluster of nerves that passes under the collarbone at the shoulder
- Ulnar nerve entrapment – pressure on the ulnar nerve as it passes behind the elbow
- Cervical or lumbar radiculopathy – pressure on the nerve roots as they exit the spinal column from the neck or lower back
Many orthopedic surgeons will order electrodiagnostic testing before recommending surgery for these conditions. It also can be used to determine the extent of an injury to a nerve after an accident and to study the effects of diseases such as diabetes. It can also show if an injured nerve is healing.