Multi-channel EEG activity correlation analysis to detect the onset of cerebral ischemia

Middle cerebral artery (MCA) occlusion was used as a model of focal cerebral ischemia in 16 cats. In order to monitor cortical electric activity, 16 channel EEG was registered referentially. Bipolar lead combinations were derived for neighboring electrodes, and the total activity was calculated as the mean square value of the time domain signal. A moving correlation window was applied to them to produce mean correlation as a function of time. All cats showed significant increase of the correlation coefficients following the event of the occlusion. It is concluded that multi-channel EEG correlation analysis may indicate the simultaneous drop of activity in most of the channels due to ischemia, therefore this method can be used as the basis of an intraoperative monitoring system.