经颅磁刺激运动诱发电位阈值的研究

An Investigation of Excitation Threshold for Motor Evoked Potentials Induced by Transcranial Magnetic Stimulation

经颅磁刺激运动诱发电位研究近年已被广泛应用于各种疾病情况下中枢运动通路功能的评定中，然而有关其阈值的定义及其测定方法尚存在不同意见，对于分别刺激左右两侧大脑半球时诱发出MEP的阈值有无差异，亦有相互矛盾的报道。本研究对该阈值的定义及测量进行了探索。对20名健康受试者的测试结果为：正常人两侧诱发拇短展肌松弛状态下MEP的刺激闭值分别为340．2％±5．6％和35．0％±5．5％，统计分析表明两者差异无显著性意义（P＞0．05），同时本研究还发现，各受试者间两侧MEP阈值的差异范围（0～5％）远较其阈值的绝对值间的差异小（25％～50％）。经颅以刺激MEP阈值的测定是一项评定运动通路传导功能的有用方法，比较两侧阈值的差异要比比较单侧阈值的绝对值差异更有意义。

The motor evoked potentials (MEP) induced by transcranial magnetic stimulation (TMS) has been widely used to investigate the functions of motor pathway in a variety of clinical conditions. Howeyer,arbitrary criteria have been adopted to define the excitation threshold for MEP and different results have been reported in regarding to the interside differences of threshold. The present paper describes the procedure we used to determine the threshold and reports the excitation threshold for MEP obtained in the relaxed abductor pollicis brevis (APB) in 20 healthy subjects. The result showed that the threshold for the MEP in the left and right AnB were 34.2±5.6% and 35.0±5.5% of the maximal output of the stimulator, respectively.Statistic analysis revealed no significant differences between the two sides. It was also found that the absolute values of threshold displayed much wider intersubject variability (25%～50% ) than the interside variability (0～5%). It is concluded that the determination of excitation threshold for MEP induced by TMS is a useful procedure for assessing the functions of motor pathway and comparison of the interside differences of threshold is more valuable than that of the absolutc values of the threshold among subjects.