Abstracts

Rationale: Sleep and epileptic activity have long been known to be closely connected and many people with epilepsy (PWE) complain about poor sleep quality. Epileptic seizures can reduce sleep quality by causing arousals as well as disturbing the sleep pattern (Takagi, 2017). In addition, inter-ictal epileptic discharges (IED) have been shown to increase before and during arousals (Peter-Derex et al., 2020). These links between epileptic activity and sleep disturbance have been investigated in short-term studies as research in the field have lacked objective methods for long-term investigation. However, recent technological advances have made it possible to obtain EEG recordings over ultra long periods and breakthroughs in computational tools have allowed the complex analysis of these big data sets. In the current case-study, we utilize these developments to investigate the longitudinal relationship between IEDs, wake after sleep onset (WASO) and sleep stage distribution.

Methods: A single person with epilepsy was monitored over 145 days with the ultra long-term subcutaneous EEG device called, the 24/7 EEG™ SubQ solution (UNEEG™ medical, Lynge, Denmark). The reported PWE was on anti-seizure medication when the recordings were initialized, and the dosage was increased almost halfway through the 145 days. Automatic algorithms were implemented to extract the sleep/wake state, the sleep stage distribution and the temporal position of interictal epileptiform discharges (IED). The nightly IED rate was computed and normalized according to the nightly amount of NREM3 sleep (NREM3-IED rate) as IEDs almost exclusively manifested during NREM3 sleep. Wake After Sleep Onset (WASO) was calculated during the first five hours of each night as an estimate of sleep disturbance. The temporal correlations between IEDs, WASO and sleep stage distribution were investigated over the course of the study.

Results: The sleep stage distribution changed over the course of the study concurrently with a reduction in NREM3-IED rate but without a simultaneous change in WASO. The person with epilepsy experienced an increase in relative amount of NREM3, NREM2 and NREM1 and a decrease in relative amount of REM while total sleep time (TST) remained unchanged.

Conclusions: The results presented here indicates that IEDs have an influence on the sleep stage distribution where fewer IEDs lead to deeper sleep. This effect was not reflected in the amount of sleep disturbance measured as WASO, which might be a sign that the mechanism linking IEDs and sleep quality is more subtle than waking. In a future study it would be interesting to investigate and implement a measure of arousals instead of WASO.

Funding: Please list any funding that was received in support of this abstract.: None.