Abstracts

Rationale: Sleep recordings are an integral part of presurgical evaluation in drug-resistant focal epilepsy. Physiological network functioning is substantially different between wakefulness and sleep and thus may add further complexity to the task of determining the epileptogenic zone (EZ). A thorough understanding of changes in epileptic networks in relation to sleep is therefore essential in order to fully appreciate the added value of sleep recordings. Furthermore, shared expertise in epilepsy and sleep is beneficial for both domains, as intracerebral EEG during presurgical evaluation offers a unique window into physiological networks and their interaction during sleep.

Methods: Here we review the current state of the literature in order to delineate the way in which sleep modifies interictal epileptic discharges (IEDs), and to summarize which sleep state is the most appropriate for aiding in discerning the EZ.

Results: Two approaches are reviewed. First, classical scalp electroencephalography (EEG) recordings help to localize the EZ, especially during REM sleep. REM sleep tends to narrow the field of IEDs, and thus helps to target the core of the EZ. Second, automated analysis of intracerebral recordings can make use of both IEDs and sleep-related oscillations in combination. In this approach, which exploits increased network interactions during sleep, NREM-sleep is the most suitable sleep stage to extract multiple features of local and distributed neuronal activity in order to predict the EZ. The added value of intracerebral recordings is perfectly bidirectional. From a sleep perspective, invasive EEG recordings are a unique opportunity to unravel local sleep-related network function of superficial and deeply situated brain structures.

Conclusions: Shared expertise in sleep and epilepsy is of mutual added value for improving the management of patients with epilepsy (Dinkelacker, El Helou, Frauscher; Revue Neurologique (Paris), 2022 May 30;S0035-3787(22)00582-3.).

Funding: V.D. is supported by a personal research grant from the John Bost Foundation. The Epilepsy Unit of the Strasbourg University Hospital is part of CRéER and EPICARE. B.F. is supported by a salary award (“Chercheur-boursier clinicien Senior”) of the Fonds de Recherche du Québec – Santé 2021-2025. Outside of the submitted work, Dr. Frauscher has received honoraria for speaker’s engagements/advisory boards from UCB and Eisai. Her lab is supported by CFI, CIHR, the Hewitt Foundation, NSERC, the Montreal Neurological Institute and Hospital, and industrial funding of Eisai.