10026-ST-2 Intraoperative neuromonitoring with direct cortical stimulation motor-evoked potentials in supratentorial glioma surgeries with preoperative moderate-to-severe motor weakness

Abstract Purpose To evaluate motor function in patients with preoperative moderate-to-severe motor weakness, we used direct cortical stimulation motor-evoked potential (D-MEP) monitoring in glioma surgeries performed in and near the primary motor cortex (PMC) and cortico-spinal tract (CST). Methods Intraoperative neuromonitoring using D-MEPs in patients with preoperative moderate-to-severe motor weakness was performed in 16 cases (14 patients). After dural opening, a single six-contact subdural strip electrode was placed on the PMC. The baseline waveform was defined as a reproducible waveform of 30 μV or higher, and a significant decrease of > 50% in the amplitude resulted in a warning. D-MEP monitoring was defined as successful if any D-MEP could be measured for either the upper or lower limb with Manual Muscle Test score below 3. Results The success rate of D-MEP monitoring in patients with preoperative moderate-to-severe motor weakness was 75% (12/16 cases) and 50% (13/26 limbs). The baseline median intensities of stimulation for D-MEPs in the upper and lower extremities were 23.3 ± 6.1 mA and 24.7 ± 9.2 mA, respectively. The 12 cases wherein D-MEP was successfully recorded in at least in one limb with moderate-to-severe motor weakness showed no deterioration of motor function postoperatively. Among the remaining four cases with unsuccessful D-MEP measurements, two showed worsened motor weakness. Conclusion D-MEP measurements in patients with preoperative moderate-to-severe motor weakness enabled motor-function monitoring without any complications, suggesting that D-MEP-based monitoring may be a reliable approach for preserving damaged motor function in glioma surgeries in and near the PMC and CST.