Electrophysiological monitoring for selective shunting during carotid endarterectomy.

Selective shunt during carotid endarterectomy is more and more widespread, but it requires a monitoring system able to identify severe brain ischemia correctly. In 255 endarterectomies for severe carotid stenosis, we evaluated cerebral activity by means of sequential use of computerized two-channel electroencephalogram (EEG) and somatosensory evoked potentials (SSEPs). In 1.96% of cases, we observed changes referable to severe cerebral ischemia: in one case, in spite of shunting, EEG asymmetry persisted till the end of the operation, and the patient awoke with irreversible aphasia. In two other cases, a progressive disappearance of the cortical wave (N20) occurred in spite of a normal EEG pattern. None of the unshunted patients had postoperative deficit. Computerized EEG is an easily interpretable method of monitoring and reveals rapidly developing cerebral ischemia, but severe SSEP changes can occur in spite of a normal EEG pattern when cerebral ischemia has a slow onset. Although SSEP monitoring is a slower method of recording, it can give a finer distinction of less severe cerebral ischemia.