Clinical electromyography: definition, application, and innovation.

Clinical EMG techniques, useful in the study of patients with neuromuscular disease, are defined. These include measurement of motor and sensory nerve conduction velocities; analysis of the size, shape, and latency of response of muscle and nerve action potentials after nerve stimulation; estimates of nerve excitability; study of the response to repetitive nerve stimulation as a measure of neuromuscular transmission; and observation of the electrical activity of muscle with needle recording electrodes (monopolar, bipolar, and multielectrodes). From a consideration of the application, limitations, and value of these various techniques, it can be concluded logically that to assure the highest probability of reliable information in regard to an individual patient, the choice of technique(s) and the part(s) to be studied should be intimately tied to a clinical analysis of that patient's problem. EMG as a fishing expedition is rarely fruitful; EMG as an exercise in clinical physiology is often exciting.