Identification of activated area after intraoperative transcranial electrical stimulation for motor evoked potential

本研究纳入患者(经颅刺激29例，直接皮质刺激35例)。随着强度的增加，从阈值水平到200 mA，潜伏期进入平台期，没有观察到潜伏期的“跳跃”。TCS和DSC的潜伏期相差很小。这些结果表明，在光强小于200 mA的情况下，TCS的激活面积几乎相同。200 mA TCS后，对侧MEP波幅明显高于同侧，提示激活区域不是脑干，而是皮质下，两侧皮质脊髓束距离较远。在两例MEP显著恶化的病例中，术后观察到对侧瘫痪。在这些病例中，相应的病变是内囊，这意味着激活的区域是内囊近端的皮质下。对于TCS-MEP监测，最好的强度被认为是超最大幅度小于200 mA所需的强度。

64 cases (Transcranial stimulation (TCS) : 29 cases, Direct cortical stimulation (DCS) : 35 cases) were included in this study. With increasing intensity from threshold level until 200 mA, the latency came to plateau, and no "jump" of latency was observed. The difference of latency between TCS and DCS was quite small. These results suggested that the activated area of TCS was almost same as far as the intensity is less than 200mA. The amplitude of MEPs after TCS with 200mA was much higher in the contralateral side compared to the ipsilateral, which suggested that the activated area was not brain stem but subcortex, where the bilateral cortico-spinal tract run distantly. In two cases in which significant deterioration of MEPs occur, postoperative contralateral palsies were observed. The corresponding lesions in these cases were internal capsula, which meant that the activated areas were subcortex which is proximal to the internal capsula. For TCS-MEP monitoring, the best intensity was thought to be the intensity needed for the supramaximal amplitude less than 200mA.