Spectral, complexity and interdependence measures of sleep EEG after ischemic stroke

The study focused on separation of sleep electroencephalogram (EEG) of patients after ischemic stroke and sleep EEG of healthy subjects. A prognostic value of the characteristics as regards patients' recovery was also studied. Many spectral measures and measures of complexity and interdependence were evaluated for EEG of 50 patients and 52 healthy subjects. The patients had higher sleep efficiency, and they spent more time in slow-wave sleep (SWS) but less time in rapid eye movement sleep in comparison to controls. During waking, high delta power relative to the reduced power of alpha and faster waves was found after stroke. During SWS, on the contrary, fewer delta waves and more of faster waves was observed in EEG ofpatients as compared to controls. The complexity of EEG ofpatients was lower during wake and higher in SWS in comparison to healthy subjects. Interdependence between the hemispheres was found to be lower for the sleep EEG of patients. It was also found that, the lower relative power in 4-8 Hz and higher relative power in 30-40 Hz of EEG 5-7 days after stroke, the worse prognosis regarding withdrawal of symptoms within the next 90 days.