Power suppression in EEG after the onset of SAH is a significant marker of early brain injury in rat models

We analyzed the correlations among membrane depolarization, changes in electroencephalogram (EEG), and histological outcome in rats in the acute stage of subarachnoid hemorrhage (SAH). SAH was induced in eight rats by cisternal blood injection, and the duration of cortical depolarization was measured. EEG power spectrums were given by time frequency analysis, and histology was evaluated. The appropriate frequency band and recovery percentage of EEG (defined as EEG recovery time) to predict the neuronal damage were determined from 25 patterns (5 bands × 5 recovery rates) of receiver operating characteristic (ROC) curves. Probit regression curves were depicted to evaluate the relationships between neuronal injury and duration of depolarization and EEG recovery. Depolarization and EEG changes on the brain cortex of rats immediately after SAH were successfully recorded. Histological study identified sixteen cites. The optimal values of the EEG band and the EEG recovery time to predict neuronal damage were 10 to 15 Hz and 40%, respectively (area under the curve [AUC]: 0.97). There was a close relationship between the percentage of damaged neurons and the duration of depolarization or EEG recovery time. These results suggest that EEG recovery time may be a predictor of early brain injury (EBI) after SAH.