A region‐specific modulation of sleep slow waves on interictal epilepsy markers in focal epilepsy

Abstract

Objective Sleep strongly activates interictal epileptic activity through an unclear mechanism. We investigated how scalp sleep slow waves (SSWs), whose positive and negative half‐waves reflect the fluctuation of neuronal excitability between the up and down states, respectively, modulate interictal epileptic events in focal epilepsy. Methods Simultaneous polysomnography was performed in 45 patients with drug‐resistant focal epilepsy during intracranial electroencephalographic recording. Scalp SSWs and intracranial spikes and ripples (80–250 Hz) were detected; ripples were classified as type I (co‐occurring with spikes) or type II (occurring alone). The Hilbert transform was used to analyze the distributions of spikes and ripples in the phases of SSWs. Results Thirty patients with discrete seizure‐onset zone (SOZ) and discernable sleep architecture were included. Intracranial spikes and ripples accumulated around the negative peaks of SSWs and increased with SSW amplitude. Phase analysis revealed that spikes and both ripple subtypes in SOZ were similarly facilitated by SSWs exclusively during down state. In exclusively irritative zones outside SOZ (EIZ), SSWs facilitated spikes and type I ripples across a wider range of phases and to a greater extent than those in SOZ. The type II and type I ripples in EIZ were modulated by SSWs in different patterns. Ripples in normal zones decreased specifically during the up‐to‐down transition and then increased after the negative peak of SSW, with a characteristically high post‐/pre‐negative peak ratio. Significance SSWs modulate interictal events in an amplitude‐dependent and region‐specific pattern. Pathological ripples and spikes were facilitated predominantly during the cortical down state. Coupling analysis of SSWs could improve the discrimination of pathological and physiological ripples and facilitate seizure localization.

Pathological neurons generate ripples at the UP‐DOWN transition disrupting information transfer

“…By contrast, in the SOZ, ripple coupling and maximal ripple‐associated firing probability occurred during the late UP‐DOWN transition, which was different from the coupling and firing in the non‐SOZ (Kuiper's V, p = 1e–3). These results included regions with interictal epileptiform discharges as part of the non‐SOZ, whereas prior investigations included these regions as part of the SOZ 27,30,37 . Thus, in the SOZ, pathological ripples occur during the UP‐DOWN transition.…”

“…These results included regions with interictal epileptiform discharges as part of the non-SOZ, whereas prior investigations included these regions as part of the SOZ. 27,30,37 Thus, in the SOZ, pathological ripples occur during the UP-DOWN transition.…”

Electrophysiological Mechanisms in the Anterior Insula Cortex during Reward Expectancy

“…The AdTech electrodes used at the Hôpital de la Salpêtrière were equipped with 4-12 contacts, each measuring 1 mm in diameter, 2.41 mm in length, and spaced 5 mm apart (Lehongre et al, 2022). Meanwhile, the HKHS electrodes employed at the Second Affiliated Hospital of Zhejiang University consisted of 8-16 contacts, with a diameter of 0.8 mm, length of 2 mm, and an inter-contact distance of 1.5 mm (Chen et al, 2023).…”

Clinical Utility of Sleep Recordings During Presurgical Epilepsy Evaluation With Stereo-Electroencephalography: A Systematic Review

“…Chen et al 36 found that IEDs and ripples were clustered around the negative peaks of sleep slow waves, and that the increase in IED and ripple densities were associated with an increase in sleep slow-wave amplitude. In addition, phase analysis showed that IEDs and ripples in the SOZ exhibited a similar facilitation by slow waves during the down state.…”

“…Eight studies evaluated the association between physiological sleep events on IEDs or HFOs and are outlined in Table 4. 5,20,25,[36][37][38][39][40] Such physiological sleep events include slow waves and sleep spindles as observed in NREM sleep, phasic REM sleep, and sleep arousals.…”