BSI versus the Eye: EEG Monitoring in Carotid Endarterectomy

Carotid endarterectomy is a common procedure as an important secondary prevention of stroke. For selective shunting, continuous EEG monitoring is a standard technique, with visual assessment to track possible ischemia. Recently, the extended BSI was proposed as a pair of quantitative features to support the visual interpretation. Here, we further evaluate its potential clinical use using a large data set. The extended BSI (consisting of a spatial and temporal symmetry measure, sBSI and tBSI, respectively) was calculated retrospectively from a group of 111 patients who underwent a carotid endarterectomy in our hospital. EEG recordings were visually assessed to determine shunt placement and compared to the calculated BSI-values. All unilateral changes in the EEG found by visual assessment are reflected by ∆-sBSI ≥ 0.060 and all diffuse changes by ∆-tBSI ≥ 0.065. In EEGs with both unilateral and diffuse changes, ∆-sBSI ≥ 0.060 and ∆-tBSI ≥ 0.065. This study extends and confirms our previous pilot results, that the sBSI and tBSI correlate strongly with the visual assessment of the EEG, as performed by experienced neurophysiologists. The extended BSI supports the visual intraoperative EEG monitoring during carotid endarterectomics and assists in a more reliable decision for selective shunting.