MULTI-CHANNEL ACTIVITY CORRELATION ANALYSIS - A METHOD TO DETECT CEREBRAL ISCHEMIA BY THE EEG

Abstract

The occlusion of the middle cerebral and the common carotid artery was used as model of ischemia. We analysed the electroencephalogram to search for features which were sensi-tive to the changes caused by reduced blood supply of the brain. Bipolar lead combinations were derived for neigh boring 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 cases showed significant increase of the correlation coefficients following the event of the occlusion. It was concluded that multi-channel EEG activity correlation analysis may indicate the simultaneous drop of activity or the drop-increase-drop sequence on most of the channels due to ischemia. This method represented a further step towards the development of a universally applicable real-time ischemia monitor which could be used under intraoperative circumstances and for long-term monitoring to help to reduce neurological risks related to the instability of the cerebral perfusion.