Motor cortex stimulation therapy for the treatment of post-stroke pain: operation method and pain alleviation mechanism

运动皮层刺激引起的皮质脊髓运动诱发电位（MEP）可以从脊髓硬膜外间隙记录。皮质脊髓MEP反应包括一个初始的d波和随后的一系列称为i波的连击。d波反映了由皮质脊髓束神经元轴突的直接激活引起的脉冲，并且对麻醉剂有抵抗性，研究人员将d波作为术中指标，在运动皮层上方的硬膜外空间放置刺激电极，用于治疗中风后疼痛。在脑卒中后疼痛患者的硬膜外空间放置一个网格电极，该电极由20个直径5mm的板电极组成，每个板电极间隔5mm，目的是利用mri引导的神经导航系统覆盖运动皮质、感觉皮质和运动前皮质。最初，在全身麻醉下，通过对每个平板电极进行阳极单极刺激来记录d波。其次，在不麻醉的清醒状态下，采用视觉模拟评分法（VAS），在单独的一天观察相同硬膜外板电极的阳极单极刺激对疼痛的减轻效果。通过对同一刺激点的网格电极记录的d波振幅与VAS的降低率进行比较，发现两者之间存在显著的相关性。所获得的结果表明，d波记录作为在运动皮层上放置刺激电极的术中指标的重要性，我们可以期待运动皮层刺激所取得的临床结果的改善。

The corticospinal motor evoked potential (MEP) evoked by motor cortex stimulation can be recorded from the epidural space of the spinal cord. The corticospinal MEP response consists of an initial D-wave and a later sequence of volleys termed I-waves. The D-wave, which reflects impulses arising from direct activation of the axons of corticospinal tract neurons and is resistant to anesthetics, was investigated as an intra-operative index for the placement of a stimulating electrode in the epidural space over the motor cortex for the treatment of post-stroke pain.A grid electrode comprising 20 plate electrodes of 5mm in diameter and each separated by 5mm, was placed in the epidural space aiming to cover the motor cortex, sensory cortex, and premotor cortex employing an MRI-guided neuronavigation system in post-stroke pain patients. Initially, the D-wave was recorded with anodal monopolar stimulation of each plate electrode under general anesthesia. Secondly, keeping the grid electrode at the same position, the effect of pain reduction induced by anodal monopolar stimulation of the same epidural plate electrodes was examined using a visual analogue scale (VAS) on a separate day in the awake state without anesthesia.A comparison between the reduction rate of the VAS and the recorded amplitude of the D-wave employing the same stimulation point of the grid electrode revealed a significant correlation. The results obtained indicated the importance of D-wave recording as an intra-operative index for placement of the stimulating electrode over the motor cortex, and we can expect an improvement of the clinical results achieved with motor cortex stimulation.