EEG as a criterion for shunt need in carotid endarterectomy

The efficacy of continuous intraoperative electroencephalographic (EEG) monitoring as a criterion for selective shunt use during carotid endarterectomy is evaluated in a group of 1661 operations in which the EEG was the sole criterion for shunt insertion. EEG monitoring is measured by the intraoperative stroke rate. Carotid stump pressure measurements were recorded as an additional observation in 1517 operations and represent a subset of the study group allowing comparison of this technique with EEG. Intraoperative stroke rate for the 1661 operations in the study group was 0.03% (five strokes). A statistically significant increase in intraoperative stroke rate was associated with the development of an abnormal EEG (1.1%), contralateral internal carotid artery occlusion (1.8%), and the combination of both abnormal EEG and contralateral internal carotid occlusion (3.3%). The EEG remained normal in 1295 operations including 75 operations with contralateral internal carotid artery occlusion. One minor intraoperative stroke (0.08%) which resolved in 1 week occurred in the absence of an EEG change with no intraoperative strokes in the 75 operations in which the contralateral internal carotid artery was occluded. Intraoperative EEG monitoring accurately (99.92%) identified patients who may safely have carotid endarterectomy without the need of a shunt.