Short and long-term prognostic value of intraoperative motor evoked potentials in brain tumor patients: a case series of 121 brain tumor patients.

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Iatrogenic neurologic deficits adversely affect patient outcomes following brain tumor resection. Motor evoked potential (MEP) monitoring allows surgeons to assess the integrity of motor-eloquent areas in real-time during tumor resection to lessen the risk of iatrogenic insult. We retrospectively associate intraoperative transcranial and direct cortical MEPs (TC-MEPs, DC-MEPs) to early and late post-operative motor function to prognosticate short- and long-term motor recovery in brain tumor patients undergoing surgical resection in peri-eloquent regions. We reviewed 121 brain tumor patients undergoing craniotomies with DC-MEP and/or TC-MEP monitoring. Motor function scores were recorded at multiple time-points up to 1year postoperatively. Sensitivity, specificity, and positive and negative predictive values (PPV, NPV) were calculated at each time point. The sensitivity, specificity, PPV, and NPV of TC-MEP in the immediate postoperative period was 17.5%, 100%, 100%, and 69.4%, respectively. For DC-MEP monitoring, the respective values were 25.0%, 100%, 100%, and 68.8%. By discharge, sensitivity had increased for both TC-MEP and DC MEPs to 43.8%, and 50.0% respectively. Subset analysis on patients without tumor recurrence/progression at long term follow-up (n = 62pts, 51.2%) found that all patients with stable monitoring maintained or improved from preoperative status. One patient with transient intraoperative TC-MEP loss and permanent DC-MEP loss suffered a permanent deficit. Brain tumor patients who undergo surgery with intact MEP monitoring and experience new postoperative deficits likely suffer transient deficits that will improve over the postoperative course in the absence of disease progression.