• G H Visser, G H Wieneke, and A C van Huffelen.
• Department of Clinical Neurophysiology, University Hospital Utrecht and Rudolf Magnus Institute for Neurosciences, The Netherlands.
• Clin Neurophysiol. 1999 Feb 1;110(2):286-94.

ObjectiveThe purpose of the study was to make an objective and quantitative analysis of the EEG changes caused by carotid artery clamping during carotid endarterectomy (CEA) monitoring.MethodsFactor analysis was used to study the intraoperative spectral EEG changes in 94 patients during clamping of the carotid artery. In addition, the relation between the extracted factors and the changes in blood pressure and blood flow velocity in the middle cerebral artery during clamping was studied.ResultsTwo factors were extracted with factor analysis. The first factor represented a change in power in the alpha and beta frequency ranges in combination with a less pronounced opposite change in power in the delta frequency range. The second factor represented a change in power restricted to the delta and theta frequencies. With the first factor, two types of spectral EEG changes could be distinguished: changes indicative of cerebral ischemia (decrease in fast activity and increase in slow activity) and the opposite changes suggesting cerebral activation (arousal). With the two factors combined, the changes indicative of minor ischemia (decrease in fast activity only) could also be distinguished.ConclusionFurther study is required to test whether patients showing the EEG changes indicative of activation or minor ischemia actually require shunting.

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