Multimodal Intraoperative Neurophysiologic Monitoring Including Transcranial Motor Evoked Potentials for the Detection of Cerebral Ischemia During Carotid Endarterectomy

PURPOSE: Carotid endarterectomy (CEA) is a common surgical intervention, but the perioperative stroke risk may be as high as 12%, with an average reported rate approximately 3%. Intraoperative neurophysiologic monitoring (IONM) can provide real-time feedback to guide the surgical team on whether or not to place a temporary shunt to reduce the length of time that cerebral blood flow is interrupted. In this study, the authors assessed the utility of adding transcranial motor evoked potentials (tcMEPs) to other IONM modalities in early detection of cerebral ischemia during CEAs. METHODS: The authors conducted a retrospective review of CEA cases from 2010 to 2020 at this center and included all CEA cases with electroencephalogram (EEG), somatosensory evoked potentials (SSEPs) and tcMEPs. The authors analyzed the IONM reports for case details. The primary study end points were types of IONM changes and their relative onsets to carotid occlusion. RESULTS: The authors identified 254 patients who underwent 274 CEAs using multimodal IONM. In 35 (12.7%) cases, there were critical IONM changes with 33 (12.0%) demonstrating changes during clamping of the carotid artery. Of these 35 cases, changes in both SSEPs and tcMEPs were observed in 20 (57.1%), only SSEP changes in 8 (22.9%), and only tcMEP changes in 2 (5.7%). In 5 cases, tcMEP loss was noted to precede other IONM changes. In total, 82% of significant changes were observed within the first 10 minutes of carotid clamping. CONCLUSIONS: This large cohort study shows that multimodal IONM with tcMEPs can contribute to the early detection of cerebral ischemia during CEA.