Outcomes of Combined Somatosensory Evoked Potential, Motor Evoked Potential, and Electroencephalography Monitoring during Carotid Endarterectomy

BackgroundWhile much has been written about multiple methods of neuromonitoring during carotid endarterectomy (CEA), there has been relatively little discussion of the use of triple monitoring via somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) in conjunction with electroencephalography (EEG). Our objective was to evaluate the rate of detection and prevention of neurologic events by multinerve SEP, MEP, and EEG in patients undergoing CEA while under general anesthesia.MethodsA prospective study of 181 consecutive patients undergoing CEA between June 2005 and September 2010 was reviewed. Intraoperative changes, including a 50% reduction in the amplitude of SEP waveforms, loss of MEP, and/or a 50% change in EEG frequency were noted as indications for shunting. This was correlated with the actual use of intraoperative shunting and postoperative neurologic sequelae at both 24 hours and 30 days. Median and tibial nerve SEPs and MEPs were also correlated.ResultsEleven patients (6%) experienced intraoperative monitoring changes (SEP: 11/11; MEP: 6/11). Five of 11 patients with MEP/SEP changes underwent shunting, while the other 6 had normalization with the elevation of their blood pressure. Of the 11 patients that had neurophysiologic changes, 54% (6/11) were patients with symptomatic disease. No patients had significant EEG changes. The total shunt rate was 2.7% (5/181). No postoperative neurologic sequelae were noted.ConclusionThe ratio of shunting at 2.7% is equal to the lowest rates reported in the awake patient literature. Interestingly, the predicted synergy of multimodality monitoring cannot be directly attributed to an increased specificity resulting from the addition of SEP and MEP to EEG, because no patients had EEG changes. In addition, in today's cost-conscious world of health care, our results do not justify implementing this particular technique of neuromonitoring across the board—but it is apparent that the combination of these 3 modalities is both safe and effective with potential applications in symptomatic patients.