15. The threshold TcMEP amplitude predicting postoperative motor defecits in intramedullary spinal cord tumour surgery

Abstract

Introduction For intramedullary spinal cord tumour (IMSCT) surgery, the ‘presence/absence’ criteria of motor evoked potentials (MEP) combined with D-wave is the most widely used type of alarm criteria for possible motor deficits. However the recent evolution of monitoring devices has changed the definition of ‘absence’of MEPs. Consequently, alarm criteria should also be reconsidered. The purpose of this study is to determine the quantifiable cut-off amplitude of transcranial motor evoked potentials (TcMEPs) for predicting postoperative motor deficits in IMSCT surgery. Material and Methods We conducted a retrospective study to examine intraoperative electrophysiological changes and postoperative motor deficits in 38 patients who underwent IMSCT surgery. Postoperative motor deficit was defined as a one point or greater decrease in MMT on the most immediate postoperative examination. Through receiver-operating characteristic curve (ROC) analysis, we identified the cut-off amplitudes for predicting postoperative motor deficits in IMSCT surgery. Cervical and thoracic lesions were compared. Results and Conclusion Among 38 surgeries, 23 were cervical and 15 were thoracic cases. Postoperative motor deficits were found in 51 muscles in 14 cases. Among 151 monitorable muscles, 17 (11.2%) showed postoperative motor deficits in cervical, and among 129 muscles, 34 (26.4%) in thoracic cases. The incidence of postoperative motor deficits were significantly higher in thoracic surgery ( p