Miniature end-plate potentials in neuromuscular disease: an electrophysiological investigation of motor-point muscle biopsies.

A technique is described for the electrophysiological investigation of motor-point muscle biopsies and the data from 13 biopsies are reported. It was not possible to demonstrate any influence of disease upon the resting potentials of individual biopsies, but resting potentials were in general lower than those reported for limb muscle in vivo. Miniature end-plate potentials (MEPPs) in clinically normal limb muscle were smaller and more frequent than those previously described in isolated intercostal muscle. In two biopsies from myasthenic patients very small amplitude MEPPs were recorded and, in one of these, MEPPs were also of very low frequency, possibly associated with the severity of the disease. The frequency and amplitude of MEPPs in muscular dystrophy and neurogenic disease have been reported and the possible significance of these findings is discussed.