Recording of Corticospinal Evoked Potential for Optimum Placement of Motor Cortex Stimulation Electrodes in the Treatment of Post-stroke Pain -Two Case Reports-

Abstract

The corticospinal motor evoked potential (MEP) evoked by motor cortex stimulation was investigated as an intraoperative index for the placement of stimulation electrodes in the epidural space over the motor cortex for the treatment of post-stroke pain. A grid of plate electrodes was placed in the epidural space to cover the motor cortex, sensory cortex, and premotor cortex employing a magnetic resonance imaging-guided neuronavigation system in two patients with severe post-stroke pain in the right extremities, a 66-year-old man with dysesthesia manifesting as burning and aching sensation, and a 67-year-old woman with dysesthesia manifesting as pricking sensation. The D-wave of the corticospinal MEP was recorded with a flexible wire electrode placed in the epidural space of the spinal cord during anodal monopolar stimulation of each plate electrode under general anesthesia. The grid electrode was fixed in position with dural sutures and the craniotomy closed. The effect of pain reduction induced by anodal monopolar stimulation of the same plate electrodes was examined using the visual analogue scale (VAS) on a separate day in the awake state without anesthesia. Comparison of the percentage VAS reduction and the recorded amplitude of the D-wave employing the same stimulation electrode revealed significant correlations in Case 1 (r ＝ 0.828, p º 0.01) and Case 2 (r ＝ 0.807, p º 0.01). The grid electrode was then replaced with two RESUME electrodes over the hand and foot areas, and the optimum positions were identified by D-wave recording before electrode fixation. Both patients reported satisfactory pain alleviation with lower stimulation voltages than usually required for patients with similar symptoms. These results indicate the potential of D-wave recording as an intraoperative indicator for the placement of stimulating electrodes over the motor cortex for pain relief.

Intraoperative changes in transcranial motor evoked potentials and somatosensory evoked potentials predicting outcome in children with intramedullary spinal cord tumors

“…The amplitude of the muscle response (D-wave) is measured. 52,53 Previous studies have specifically examined D-wave amplitude changes and have shown that a 50% decrease reliably predicts postoperative motor deficit. 36 While informative, D-waves are not perfect.…”

Motor cortex stimulation for facial chronic neuropathic pain: A review of the literature

“…described in two patients the D-wave of the MEP as an intraoperative indicator for the placement of stimulating electrodes over the motor cortex for pain relief, the percentage VAS reduction was significantly correlated with the D-wave amplitude, indicating that D-wave recording provides and intraoperative guide for placing the stimulating electrode at the optimum position on the motor cortex. [124]…”

Changes in Motor Function Induced by Chronic Motor Cortex Stimulation in Post-Stroke Pain Patients

“…It is reported that the D-wave of corticospinal MEP reflects impulses arising from the direct activation of the axons of corticospinal tract neurons, and the D-wave is recorded only when the primary motor cortex is stimulated [19][20][21]25] . Unlike muscle responses to motor cortex stimulation, the D-wave is resistant to surgical doses of anesthetics and is unaffected by muscle relaxants, apart from changes in the excitability of spinal motoneurons, and it is easy to compare the amplitudes related to the site of cortical stimulation [19][20][21][25][26][27] . On the basis of these findings, we carried out D-wave monitoring to select the best location of the stimulation electrode in this study.…”

“…How to place the cortical stimulating electrode is also important in MCS therapy. Various surgical techniques for the accurate placement of epidural electrodes over the motor cortex have been reported [3,6,11,19] . For the placement of epidural electrodes, a structural and functional magnetic resonance brain imaging (MRI and fMRI, respectively) procedures were used in the multicenter studies to verify the anatomical location of the stroke and to identify the cortical area of functional activation ipsilateral to the stroke within the primary motor cortex that is associated with the voluntary movement of the affected hand [16][17][18] .…”

“…We can monitor muscle-evoked potential in response to MCS: however, it is usually disturbed in patients with severe motor weakness and is carried out under general anesthesia. Corticospinal motor-evoked potential (MEP) evoked by the direct stimulation of the motor cortex can be recorded from the epidural space of the spinal cord [19,20] . The D-wave of the corticospinal MEP has been used for the intraoperative identification of the primary motor cortex and for the intraoperative monitoring of motor function, because the D-wave is evoked by the direct activation of subcortical pyramidal tract neurons and is not suppressed by general anesthetics and muscle relaxants [19][20][21] .…”