UNIPOLAR ELECTROMYOGRAMS OF NORMAL AND DENERVATED HUMAN MUSCLE

Abstract

The form of human muscle action potentials as recorded with a unipolar needle micro-electrode with exposed tip about 30 u is described. The typical form of a single unit is a triphasic wave. This is composed of a large negative spike 1.5-3 msec, in duration preceded and followed by positive waves of variable size and duration depending upon the site of the needle point in the path of the conducted wave of muscle action potential. Irregularities may appear on the negative spike due to slight dysynchrony of its component fiber potentials but unit spike duration longer than 5 msec, was not found in normal muscle, the avg. being about 2 msec. Fiber potentials from denervated muscle were of the order of 1 msec, in duration with a range between 0.5 and 1.5 msec. In denervated sensitized muscle, nonpropagated waves of positive sign were obtained following injury at the needle point. Complex wave forms of longer duration in normal muscle were found due to grouped firing of several units and/or repetitive firing of single units. Polyphasic forms of longer duration in muscle re-innervated following a nerve lesion were considered due to extensive ramifications of terminal arborizations in regenerating nerves, and to lack of maturation in these fibrils with possibly non-uniform prolongation of endplate delays.