Abstract TP80: Improving Perioperative Stroke Detection During Intracranial Aneurysm Surgery Using Somatosensory Evoked Potential Waveform Analysis

Abstract

Background: Current alarm criteria for evaluating impending perioperative stroke using somatosensory evoked potential (SSEP) intraoperative monitoring is a 50% reduction in amplitude or a 10% increase in latency. In this study, we aim to evaluate the diagnostic accuracy of SSEP changes for predicting perioperative stroke during intracranial aneurysm surgery. Methods: We retrospectively reviewed the intraoperative neurophysiological records of 100 patients who underwent intracranial aneurysm clipping at our institution between 2009-2013. Of those 100 patients, 25 patients incurred a new onset perioperative stroke and 75 age- and sex-matched controls did not. Quantitative analysis was done to evaluate SSEP amplitude and latency changes during various surgical events including pre-incision, incision, dural opening, before clipping (both temporary and permanent), after clipping, and during dural closure. Diagnostic accuracy was calculated as the area under the receiver operating characteristic curve (AUC) for maximum SSEP amplitude and latency changes from a baseline set at incision. Statistical analysis was performed using R Statistical Software v3.4.1. Results: The mean age (with standard deviation) of our cohort was 55.3 ± 11.2 yrs (24 male, 76 female). Preoperative rupture rate was similar in patients with perioperative stroke (36%) and controls (25%) (p=0.440). SSEP amplitude reduction was significantly greater in patients with perioperative stroke relative to controls after temporary clipping (54.6% vs. 24.3%, p<0.001). AUC for maximum amplitude reduction was calculated to be 0.80 (95% CI, 0.70-.0.90). Notably, latency prolongation was found to be a non-significant discriminator of stroke, with an AUC of 0.60 (95% CI, 0.47-0.73). AUC for 50% SSEP amplitude reduction was calculated to be 0.73 (95% CI, 0.63-0.84) and the AUC for 10% latency prolongation was found to be 0.54 (95% CI, 0.44-0.64). Conclusion: SSEP amplitude changes, but not latency changes, are strongly predictive of stroke during intracranial aneurysm surgery. However, the current alarm criteria of 50% reduction in amplitude have limited value in informing the surgeon of impending perioperative stroke due to their predictive nature.