Motor evoked potentials (MEP) during brainstem surgery as predictor of postoperative corticospinal function

Background: Brainstem surgery bears a risk of damage to the corticospinal tract (CST). Motor Evoked Potentials (MEP) are used intraoperatively to monitor CST function in order to detect CST damage at a reversible stage and thus impede permanent neurological deficits. However, warning criteria in this context are not generally agreed on. Methods: We analysed 104 consecutive patients who underwent microsurgical resection of lesions affecting the brainstem (58 intraaxial, 44 extraparenchymal). Motor grade was documented prior to surgery, early postoperatively and at discharge. MEP was recorded after transcranial el…