These test are considered electro-diagnostic studies of nerves and are commonly performed in patients with suspected nerve and muscle injury due to trauma, disease, nerve compression and other associated diseases.
EMG stands for Electromyography and is use to evaluate the electrical activities of muscles, which are innervated (connected to nerves) by specific nerves which may be irritated or damaged. By studying the muscle electrical activity, we can determine the extent of nerve damage or degeneration. It consists of injecting a fine needle (electrode) into a specified muscle in the extremity, neck or back. The electrode is connected by a cable to a computer, which in turns records the electrical activity of the muscle at rest and during stimulation. The information is then displayed as a graphic and digital format. Based on this information, the physician can accurately assess the presence of nerve damage.
NCV stands for Nerve Conduction Velocity and is performed to evaluate how well the nerves conduct an electrical impulse. The nerve is electrically stimulated at different sites during its course throughout the neck-arm, back-legs, etc. The response is recorded by electrodes placed along the nerve pathway and transmitted to a computer. According to the results generated by the computer, the physician will be able to interpret the results and properly diagnosed the condition.
An EMG takes about 45 minutes to an hour to complete. The nerve conduction studies are commonly performed first, followed by the EMG. The electrical stimulations used in nerve conduction studies typically feel like getting a rubber band snapped against your skin. Usually, 3-6 nerves are tested in an affected limb and, if necessary, a few in an unaffected limb are tested for comparison. The EMG feels like getting your skin pinched with electrode insertion and may cause a dull ache, but is generally well tolerated. Generally, nine to twelve muscles are tested. Arm, forearm, and hand muscles are tested to evaluate neck and upper limb injuries. Thigh, leg, and foot muscles are used to evaluate low back and lower limb injuries. Risks of an EMG are very rare. It may hurt a little at the time of the test, but this discomfort does not last long.