RESUMO
INTRODUCTION: Carotid endarterectomy is a common procedure as a secondary prevention of stroke, and one of the early controversies in carotid surgery is centered around whether a shunt should be used during this procedure. Although various EEG parameters have been proposed to determine if the brain is at risk during carotid artery clamping, the common procedure is still the visual assessment of the EEG. We propose a brain symmetry index (BSI), that has been implemented as an on-line quantitative EEG parameter, as an additional criterion for shunt need in carotid endarterectomy. METHODS: The BSI captures a particular asymmetry in spectral power between the two cerebral hemispheres, and is normalized between 0 (perfect symmetry) and 1 (maximal asymmetry). The index was evaluated retrospectively in a group of 57 operations in which the EEG and the transcranial Doppler were used as criteria for shunt insertion. In addition, after online implementation of the algorithm, several patients have been evaluated prospectively. RESULTS: If no visual EEG changes were detected, it was found that the change in BSI from baseline, DeltaBSI