Neuronal activity and cortical perfusion determined by quantitative EEG analysis and laser doppler flowmetry are uncoupled in brain injured rats

Abstract

Following traumatic brain injury uncoupling of metabolism from perfusion, reflected by an increase in cellular activity in face of reduced perfusion contributes to secondary tissue damage. Standard autoradiographic techniques employed to study metabolism and perfusion are limited by the inability to perform longitudinal investigations. Therefore, the aims of this study were to investigate if metabolic uncoupling can be studied by applying noninvasive and non-radioactive methods. For this, quantitative EEG analysis and laser Doppler flowmetry were employed to determine changes in EEG activity as a global measure of neuronal activity and pericontusional cortical perfusion during the early phase following controlled cortical impact injury (CCII). In eight rats changes in neuronal activity and pericontusional cortical perfusion were determined before, at 4 and 24 hours after CCII. Neuronal activity was significantly increased by 40% at 4 hours after CCII followed by a significant decrease by 60% at 24 hours compared to pre-trauma levels. Pericontusional cortical perfusion was significantly reduced by 45% and 18% at 4 and 24 hours after CCII. respectively. Non-radioactive methods like quantitative EEG analysis and laser Doppler flowmetry can be used to reveal underlying uncoupling of EEG activity from cortical perfusion which is mostly sustained in the early phase following CCII.