Electrophysiological estimation of the number of motor units within a human muscle. Jo,arnal of Neurology, Neurosurgery and Psychiatry

SUMMARY An electrophysiological method is described for estimating the numbers of motor units in the extensor digitorum brevis muscle in man. The results obtained are compared with counts of axons in the nerve to the muscle. The significance of the sizes of the evoked motor unit potentials is discussed. There is, at present, no satisfactory method for assessing the extent of denervation in human muscles during life. Thus, analysis of the density of the electromyographic interference pattern during maxi-mum effort, although a valuable procedure in skilled hands, is not usually quantitative (see, however, Rose and Willison, 1967). In addition, it has the dis-advantage of requiring the full cooperation of the patient and the maximum density depends on both the physical properties of the recording electrode and the muscle selected for study