Objective

The present study investigated the effects of the stimulus polarity and location of motor evoked potential (MEP) to establish a stimulation protocol.

Methods

Nineteen patients who intraoperatively underwent MEP in bipolar direct cortical stimulation were enrolled in the present study. Somatosensory evoked potentials (SEP) of the contralateral median nerve stimulation were recorded to determine stimulation sites. MEP was performed under two settings in all patients: 1. Anodal bipolar stimulation: an anode on the precentral gyrus and a cathode on the postcentral gyrus, 2. Cathodal bipolar stimulation: a cathode on the precentral gyrus and an anode on the postcentral gyrus. MEP amplitudes and the coefficient of variation (CV) at a stimulation intensity of 25 mA and the thresholds of induced MEP were compared between the two settings.

Results

An electrical stimulation at 25 mA induced a significantly higher amplitude in cathodal bipolar stimulation than in anodal bipolar stimulation. Cathodal bipolar stimulation also showed significantly lower thresholds than anodal stimulation. CV did not significantly differ between the two groups.

Conclusions

These results indicate that cathodal bipolar stimulation is superior to anodal bipolar stimulation for intraoperative MEP monitoring.

Significance

MEP in cathodal bipolar cortical stimulation may be used in a safe and useful evaluation method of motor fiber damage that combines sensitivity and specificity.

中文翻译：

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双极感觉运动直接皮层刺激极性对术中运动诱发电位的影响

客观的

本研究调查了刺激极性和运动诱发电位 (MEP) 位置的影响，以建立刺激方案。

方法

本研究招募了 19 名术中接受双极直接皮层刺激的 MEP 患者。记录对侧正中神经刺激的体感诱发电位 (SEP) 以确定刺激部位。MEP 在所有患者的两种设置下进行：1. 阳极双极刺激：中央前回的阳极和中央后回的阴极，2. 阴极双极刺激：中央前回的阴极和中央后回的阳极。在 25 mA 刺激强度下的 MEP 幅度和变异系数 (CV) 以及诱导 MEP 的阈值在两种设置之间进行了比较。

结果

与阳极双极刺激相比，25 mA 的电刺激在阴极双极刺激中诱导了显着更高的振幅。阴极双极刺激也显示出明显低于阳极刺激的阈值。两组之间的 CV 没有显着差异。

结论

这些结果表明，对于术中 MEP 监测，阴极双极刺激优于阳极双极刺激。

意义

阴极双极皮层刺激中的 MEP 可用于结合敏感性和特异性的安全且有用的运动纤维损伤评估方法。