Excitablity of spinal anterior horn cells after transcranial magnetic stimulation – Measurement of the excitation suppression time in spinal anterior horn cells after median nerve electrical stimulation – *
Few studies have previously evaluated the suppression time following excitation of spinal anterior horn cells. Therefore, using 93 healthy adult volunteers, we evaluated whether the anterior horn cells were re-excited by transcranial magnetic stimulation (TMS) following initial excitation after electrical stimulation (ES) of peripheral nerves. When motor evoked potentials (MEPs) were independently recorded using surface electrodes, concentric needle electrodes, or single fiber needle electrodes, there were no significant differences in the electrical potentials obtained by the three types of electrodes. When waveforms after the occurrence of collision in the distal to the anterior horn cells were compared to those obtained after TMS alone, the latency by the collision technique was significantly longer than that by TMS alone. When the anterior horn cells were excited by ES before the arrival of TMS, the latency was prolonged in many subjects. These findings suggest that the recording of previously reported descending volleys on muscle fiber membrane is questionable. A lot of anterior horn cells may be inhibited for more than 10 ms after ES to peripheral nerve. (Accepted on October 16, 2001) Kawasaki Igakkaishi 27(4): 293-303, 2001
