2. A record of the spiking electrical discharge of a muscle, motor unit, or muscle fiber generated in response to neutral impulses or arising spontaneously.
3. A record of eye movements when reading, obtained by measuring the potential difference between an electrode placed at the center of the forehead and one placed at the temple.
4. A record of the intrinsic electric activity in a skeletal muscle.
Such data aid the diagnosis of neuromuscular problems and are obtained by applying surface electrodes or by inserting a needle electrode into the muscle and observing electric activity with an oscilloscope and a loudspeaker.
Some electromyograms show abnormalities; such as, spontaneous electric potentials within the muscle under study, and help pinpoint lesions of motor nerves.
Electromyograms also measure electric potentials induced by voluntary muscular contraction.
2. An umbrella term for the entire electrodiagnostic study performed in the EMG laboratory, including not only the needle electrode examination, but also the nerve conduction studies.
3. A diagnostic procedure in which metal probes are attached to or inserted into the skin in order to detect the electrical activity of contracting muscles.
Such activities are altered in recognizable ways by diseases that affect either muscles or nerves which supply the muscles.
4. The preparation, study of, and interpretation of electromyograms.5. The recording of electrical activities associated with muscular functions, often used in the clinical diagnosis of muscular disorders.
A single electrical spike potential is generated when a muscle fiber contracts while the magnitude of the spike potentials is roughly proportional to the amount of muscular tension.
Surface detecting electrodes (for many muscle fibers) or needle electrodes (for one or a few fibers) provide a signal that is amplified and displayed on a cathode-ray tube.