RESUMO
This experimental study was designed to develop an electromyography(EMG) machine and a program to be used during the selective dorsal rhizotomy, and to investigate the patterns of EMG waves generated by stimulation of the normal spinal nerve roots in cat. The developed machine, consisting of nerve stimulator, EMG amplifier, analogue-digital converter and computer program, functioned well during experiment without any mechanical or electrical problems. We were able to record pure H-wave(Hoffmann wave) in EMG by stimulating posterior root in most cases, although components of motor and directly conducted waves were observed only in few cases. The peak latency of H-wave, which was about half of that of the motor wave by the mean value, was consistent as a whole. H2/H1 ratio (the ratio of the second and the first H-wave), peak amplitude and the pattern of changes of the peak amplitudes with continuous sitmulation, however, varied greatly from case to case. In conclusion, the results of this experiment suggest that EMG wave patterns, generated by the stimulation of the posterior nerve roots, may not be appropriate for the determination of the nerve roots to be cut during the selective dorsal rhizotomy.