Approximate entropy of EEG as a measure of cerebral ischemic injury.

No doubt a noninvasive technique for detection of focal cerebral ischemic extent, before the focus is formed, is extremely valuable. A new approach to cerebral ischemic state analysis by approximate entropy is described in this paper. After a brief introduction to the concept, the approximate entropy, ApEn, were extracted from two different EEG time series, based on a novel cerebral ischemia experiment model of SD rat. Then the entropy values were analyzed, and the results showed that this measure of EEG complexity is sensitive to the extent of ischemic cerebral injury, ischemic and normal region can also be distinguished.