抄録
Intraoperative motor evoked potential monitoring using transcranial electrical stimulation (TC-MEP) has been used to prevent postoperative motor deficits. However, postoperative motor deficits without intraoperative TC-MEP changes, (false negative MEP results), have been reported. We hypothesize that false negative TC-MEP results are a consequence of inadequate stimulation of the corticospinal tract. To activate the motor cortex only, stimulation intensity can be set at 20 V above the threshold level. Optimization of stimulation intensity resulted in fewer false negative TC-MEP results. In addition to stimulation intensity, there are three important points to be considered during intraoperative TC-MEP monitoring. First, stimulation threshold levels fluctuate during surgery; therefore, the threshold must be measured at each stage of the operation. Secondly, muscle evoked potentials must be recorded from the ipsilateral side as well as the contralateral side. Finally, when TC-MEP is recorded from the ipsilateral side, we should doubt TC-MEP findings.
