The use of the electromyograph (EMG) in clinical diagnosis is now firmly established. Its application in human neurological disorders was described in 1938 by Denny-Brown and Pennybacker.1 It has been, however, only in the past 12 years that the specific value of the instrument has gained widespread recognition.* This field of clinical electromyography has been covered in excellent fashion by Marinacci in his monograph published in 1955. All workers have noted that the EMG is a laboratory instrument which supplements, but obviously cannot replace, accurate clinical examinations.
The technical accuracy of electromyography depends on two primary factors: a trained electromyographer and an instrument of high fidelity. This instrument should consist of a cathode ray oscilloscope, a sensitive sound amplifier, and methods for permanently recording the electromyogram obtained (tape recording and synchronized cameras). A fine monopolar needle electrode inserted directly into skeletal muscle is used to pick up normal or