EEG-Derived biomarkers for daytime sleepiness in patients with chronic stroke

Stroke patients with motor deficits often report daytime sleepiness. While slowing of the EEG during wakefulness has been shown after stroke, it is unknown if and how this is linked to their perception of sleepiness. Using waking EEG and a motor task (associated with mild sleepiness), we examined: 1) differences in the frequency composition and lateralisation of the EEG between stroke patients and controls, and 2) the relationship between the EEG and subjective sleepiness ratings. EEG and Karolinska Sleepiness Scale (KSS) data were collected from 15 right hemispheric stroke patients and 15 matched controls before and after a motor priming task. Frequency analysis was performed on C3 and C4 channels. Prior to the task, the stroke group revealed increased power density below 10 Hz compared to controls for both hemispheres, with more pronounced effects within the lesioned hemisphere. The motor task significantly increased KSS scores in both groups. Increased beta and alpha activity was observed after the task in the control group. The stroke group showed post task increases in beta activity for the non-affected hemisphere and bilateral increases in alpha and theta activity. An association between KSS and the EEG was observed post task in the stroke patients within the theta and alpha bands. Therefore, slowing of the EEG is related to perception of daytime sleepiness in stroke patients. This effect may not have been observed in the controls due to the way in which the motor task manipulates sleepiness within each group, as it is more challenging for those with motor deficits