2-3-13. Components analysis of transcranial electrical stimulation motor evoked potentials

Abstract

Muscle action potentials induced by transcranial electrical stimulation (TCSMEP) are well used to know the impairment of motor function under general anesthesia. Though the components of waveforms are not known. We analyzed the origin or meaning of TCSMEP waveforms. All data were obtained from gastrocnemius with a pair of needle electrodes (belly-tendon method) during six times spinal surgeries (intramedurally tumor 5, disk herniation 1). Waveforms consisted of the initial negative spiky wave’s complex (INSWC) and the dull wave of the latter half (LHDW). The smallest negative peak amplitude (SNPA) had positive correlation with the average of other negative peak amplitudes among the initial wave complex. And SNPA is not affected by the fluctuation of positive waveforms. SNPA seemed to be suitable for the indicator of intraoperative monitoring. Furthermore, there was a positive relationship between SNPA and the positive peak amplitudes of LHDW. LHDW seemed to show the difference of electrical potentials that resulted from the shortening of gap distance while the muscle contracted. TCSMEP waveform may consist of major 2 parts at least. INSWC is electrical activity around EC junctions. LHDW is mechanical activity of muscle contractions. These findings are helpful to evaluate and assess TCSMEP precisely.