O181 Usefulness of transcranial motor evoked potential during surgery for gliomas located close to the motor pathway

Abstract

Objectives To determine whether motor evoked potential (MEP) provide reliable monitoring of the motor system during resection of gliomas adjacent to the motor pathway. Method 74 patients underwent MEP monitoring during surgery (47 males, 27 females; age range, 0–84 years; median age, 58 years). We examined two items. First of all, we evaluated whether the rate of amplitude changes and postoperative motor outcome were correlated. In the next study, we defined the rate of MEP changes in affected hemisphere as ‘A’, and the ratio of MEP changes in unaffected hemisphere as ‘B’. We also researched whether the A/B ratio and postoperative motor outcome were correlated. Result MEP recordings were stable in amplitude during surgery in 67 patients (90.5%). No postoperative motor deficit was found in 41 out of 67 patients. However, postoperative paresis developed in 26 (38.8%) patients and 15 (22.4%) of them left paralysis after 1 week later. In the paresis developed group, MEP decrease in amplitude (>50%) occurred in 5 patients (33.3%), while decline A/B ratio ( Conclusion During surgery for gliomas close to the motor pathway, we first should pay attention to the MEP change rate. When the amplitude decrease 50% or less, we conclude that operation should be stopped and the A/B ratio (