Stroke-related EEG changes during carotid surgery.

EEG recordings from 230 carotid endarterectomies performed with an automatic EEG monitoring system were reviewed with the purpose of establishing the exact relation between EEG changes and intraoperative stroke. Patients were selectively shunted, based on the EEG changes occurring after carotid cross-clamping. Transient EEG asymmetry was not associated with intraoperative stroke. Only persisting EEG asymmetry reflected intraoperative major stroke, expressed by a positive predictive value of 0.50, but also in terms of specificity (0.99), sensitivity (0.80) and diagnostic gain (47.8%) of the EEG; minor strokes could not be detected with EEG monitoring. Analysis of the time course of the persisting asymmetry confirmed the thrombo-embolic origin of the majority of the major strokes.