同時記録筋電図によるkinetic及びtonic NMUの分析ならびに各unitの分布に関する研究

(1) Duration and Voltage of normal motor unit potentials of several muscles in human subjects were measured. The durations observed were ranged from 1 msec to 14 msec and the amplitude from 100 μV to 1600 μV. Generally, the large muscles show higher voltage than the small, and the proximal muscles are higher than the distal. In the upper extremity, the extensors show higher voltage than the flexors but in the lower extremity, the flexors are higher than the extensors. Though there was no obvious difference on the duration observed in the different muscles, the extensors showed longer duration than the flexers in the upper extremity and the flexors are longer than the extensors in the lower extremity. But, both of the durations and the voltages measured could not be classified into two groups, the kinetic and the tonic motor units. (2) In the study, an observation was made during minimal contraction of flexor digitorum profundue muscle and the results were as follows: a) Small diphasic spikes which showed symmetrical form of positive phase and negative phase were obtained with bipolar concentric needle electrode. Amplitudes of these spikes were ranged from 80 μV to 220 μV, and their durations from 1 msec to 4 msec. b) These symmetrical and diphasic spikes are classified into two groups; one is sharp spike with short duration, and the other is slow wave with long duration. c) The former is considered as the kinetic motor unit while the later as the tonic motor unit. d) Two spikes which were picked up from two different points in the same muscle during minimal contraction (This study was carried out in the two different direction along the muscle. In one experiment, these two electrodes were placed rectanglar to the muscle axis and the distance between them was 2 cm and in the other, electrodes were put along the muscle axis and the distance was 2.5 cm.) The spikes from these two points were synchronized each other. and showed the same duration. These results may indicate that the distribution of one motor unit covers relatively wide area in the muscle innervated. (3) Further examinations were carried out on 4 patients with spinal cord tomur and one with amyotrophic lateral sclerosis. The results were as follows: a) Small diphasic spikes were seen in paralysed muscle of the patients with spinal cord tumor. b) Regulation of the frequency of these small diphasic spikes was fairly good. These spikes disappered when the patient stopped his voluntary contraction of the mucle tested and were clearly differentiated from the fibrillation potentials firing spontaneously at rest. c) There are two different wave forms observed in these small spikes, one is sharp spike with short duration, the other is slow wave with long duration. Voltages of the former type are 100 μV to 400 μV and durations are 1 msec to 2 msec. The later type shows voltages of 80 μV to 100 μV, and durations of 2 msec to 4 msec. d) The sharp spike is considered to be taken from the kinetic motor unit, and the slow wave from the tonic motor unit. e) Two types of spike were observed in paralysed muscles of the patient with amyotrophic lateral sklerosis. (1) Voltage: 100 μV, duration: 1.5 msec and (2) Voltage: 400 μV, duration: 2 msec. In this patient histolgical examination was done by means of biopsy on the muscle tissue where the electrode was placed. Around the tip of the electrode, there were intact white muscle fibers observed among degenerated red fibers. It is considered from this examination that these two sharp spikes were taken from the intact white muscle fibers, kinetic motor unit.