MUSCLE FIBER CONDUCTION VELOCITY USING A SPIKE-TRIGGERED AVERAGING TECHNIQUE; SIZES OF RECORDING SURFACE ELECTRODES
Akio Tsubahara, Sadanori Kawamoto, Ken Akashi (Kawasaki Medical School, Kurashiki, Japan)
Purpose: Although some methods for the measurement of muscle fiber conduction velocity (MFCV) in muscle diseases as well as in disuse muscular atrophy have been previously reported, a sizable amount of time is required to calculate MFCV. This study was performed to investigate whether a method using a spike-triggered averaging technique reported by Masakado et al, could be useful for routine measurement of MFCV in clinical electrodiagnosis.
Method: MFCV was measured in the biceps muscles of five healthy volunteers. A concentric needle was inserted into the shallow part of each muscle as a trigger electrode, and averaged motor unit action potentials (MUAPs) were recorded from four surface electrodes parallel to the muscle fibers. MFCVs were calculated from the time lags of the peak latency of the four MUAPs In this study, we compared the arrays of MUAPs recorded by surface electrodes of three sizes; 1 cm, 4 mm, and 0.5 mm in diameter.
Result: The time lags in the peak latency of the four MUAPs could be distinguished from each other easily using nail-type electrodes (0.5mm in diameter). Since the peak of the four MUAPs formed a queue in most of the trials using the electrodes of 1 cm in diameter, it is suggested that the large size electrodes picked up the electrical current generated in wide area.
Conclusion: The spike-triggered averaging technique proved to be a useful method for measuring MFCVs when the recording electrodes are small.
THE MOTOR UNIT NUMBER ESTIMATION (MUNE) IN STROKE PATIENTS
Yukihiro Hara, Kazuto Akaboshi, Toshiyuki Fujiwara (Murayama National Hospital, Tokyo, Japan), Naoichi Chino (Keio University, Tokyo, Japan)
It is reported that submaximal stimuli can evoke a sample of S-MUAPs in the F- response entirely representative of the relative numbers of surface detected motor unit action potentials (S-MUAP) of different sizes. The MUNE was investigated among the hemiplegic and non-hemiplegic upper extremity muscles in ten stroke patients with moderate-to-severe hemiplegea. The average S-MUAP on each abductor policis brevis (APB) muscle was calculated from a selected population of many F-wave responses. The MUNE was calculated by dividing the peak-to-peak amplitude measured from the average S-MUAP wave form into corresponding values measured from a maximum M-potential. The impaired side motor unit number was compared with the control side. The motor unit number on the hemiplegic side was significantly lower than on the control side (P<0.05, paired t-test). This conclusion suggested that the motor unit could decrease in the moderate-to-severe hemiplegic upper extremity after stroke.