Alterations of sleep oscillations in focal epilepsy patients: A combined polysomnography-high density EEG study

• Applicant: Dr. Katharina Schiller
• Subject Area: Clinical Neurology; Neurosurgery and Neuroradiology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 507037359

Sleep and epilepsy are linked in a bidirectional and complex way. On the one hand, disturbed sleep is known to aggravate epilepsy, whereas on the other hand, epilepsy has a negative impact on sleep. Sleep macro- and micro-architecture were found to be disturbed in epilepsy patients, and certain sleep stages were found to either promote or inhibit epileptic activity. Seizures and interictal epileptiform discharges (IEDs) are facilitated by non-rapid eye movement (NREM) sleep, whereas during rapid eye movement (REM) sleep, the likelihood of seizures and IEDs is decreased. NREM sleep is characterized by specific oscillations such as slow waves and sleep spindles which reflect physiological neuronal activity within cortical-subcortical networks and underlie several sleep-related functions. These sleep oscillations were found to play an important role in memory and cognition. Especially procedural and declarative memory as well as processing speed as one subscale of the intelligence quotient were positively correlated with spindle activity. Existing evidence points to the fact that sleep oscillations might be altered in epilepsy, but the extend of these disturbances and their fluctuation overnight remain unknown. Therefore, the objective of our study is to provide a mapping of NREM sleep oscillations in patients with focal epilepsy by comparing high-density electroencephalography (HD-EEG) full night recordings obtained in 25 patients with drug-resistant focal epilepsy compared to 25 healthy controls. We hypothesize that i) there are alterations of NREM sleep oscillations in epilepsy patients compared to controls and they are stronger in focus close (the same lobe) areas than in focus remote areas, ii) the effect of alterations of NREM sleep decreases overnight due to the influence of homeostatic factors as seen for physiological sleep phenomena (for example slow wave power), iii) the area with the highest extent of alterations of NREM sleep oscillations matches with the epileptic focus, iv) the number of IEDs is positively correlated with the severity of alterations of NREM sleep oscillations, and v) the extent of alterations is negatively correlated with neuropsychological performance such as memory and executive functioning. This research project will add significantly to the field of sleep and epilepsy by contributing to understand sleep disorders and memory issues frequently encountered in epilepsy patients and by delivering new impulses for epilepsy therapy and disease management.

• DFG Programme: WBP Fellowship
• International Connection: Canada
• Host: Professorin Dr. Birgit Frauscher