Electromyography (EMG) and Nerve Conduction Velocity Studies (NCS) studies are ordered to evaluate for injury or disease of muscle, nerve roots, and peripheral nerves.
They test the condition of the nerves from the spine, face, and extremities, including the foot and hand. These studies are normally done together and are usually performed as a workup for complaints of pain, weakness, numbness, or tingling.
Common problems tested include:
An EMG records and analyzes the electrical activity in your muscles. It is a diagnostic study in which specific muscles are stimulated to look for abnormal electrical signals in the muscles. If the muscles are not working properly, it can be assumed that the nerves are being irritated, pinch, functioning abnormally, or are damaged. EMG’s provide information about the presence of nerve injury and extent of a patient’s problem. EMG’s can differentiate an old injury from a new injury.
During an EMG, small, thin needle electrodes are placed in the muscle to record the electrical activity. When the needles are inserted, you may feel some pain and discomfort. The doctor will ask you to relax the muscle and to tense it slightly. The doctor will listen and watch a TV-like screen that broadcasts the electrical signals. You will also be able to hear the signal sounds as you move the muscle. If you relax during the procedure, the discomfort will be minimal. 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.
NCS (Nerve Conduction Velocity Studies) record the responses of sensory and motor (muscle) nerves in the extremities (arms and legs) to electrical stimulation. These studies are used to identify and aid in the diagnosis of entrapment syndromes (pressure on the nerves), peripheral nerve lesions and neuropathies (diseases of the nerves). This test also helps identify muscle problems. The nerve is given an electrical stimulation, and the speed of the impulse is measured, recorded and evaluated.
Nerves are stimulated with a small amount of electricity and the responses are recorded using small electrodes. Some of the electrodes are small metal discs and some are wires that slip around the finger. As the current travels down the nerve pathway, the electrodes placed along the way capture the signal and time how fast the signal is traveling.
Although you may initially be startled by the suddenness of the stimulation, it is not painful and most people are comfortable during the testing procedure. It may feel a little “weird” since it will sometimes make the fingers or toes “twitch.”
Electrodiagnostic testing also can be used to determine the extent of injury to a nerve after an accident and to study the effects of diseases such as diabetes. Your health insurance company or HMO may require electrodiagnostic testing to confirm a diagnosis before authorizing medical or surgical treatment.