格子状表面電極によって測定した神経筋接合の配置

抄録

Motor unit action potentials were derived with multiple surface electrodes from the biceps brachii of 3 healthy adults. The electrodes comprised a 9-by-16 grid array of small gold-coated metal contacts attached to a cylindrical plate. The spacing of the contacts was 5.08mm in the direction of muscle fibers and 2.54mm in the muscle circumference. With this electrode assembly 128 channels of myoelectric signals were derived simultaneously. Individual signals were derived bipolarly from a pair of contacts adjacent in the direction of muscle fibers. These signals were sampled by a computer, displayed on a graphic terminal, plotted on a chart and analyzed visually. The myoelectric signals showed motor unit action potentials propagating along the muscle fibers. The mechanism of the generation of motor unit action potentials indicates that the source of the propagation marks the location of myoneural junctions. In each subject the measurement was repeated 20-30 times by changing recording positions and contraction levels. These records were combined to draw a topographical map of myoneural junctions over the whole surface of the biceps. The map of myoneural junctions showed the innervation zones consisting of 6-13 separate areas and lying at the middle length of the biceps in a band 30-60mm wide. The number and the size of these areas varied between subjects. This technique of multiple surface electrodes has an advantage over conventional EMG techniques, e.g. spectral analysis, in that the measurement clarifies the anatomical structure of the muscle and the results are not affected by the electrical characteristics of the instrumentation devices. This technique should become effective in the diagnosis of neuromuscular disorders and in developing new application fields of surface EMG.