Quantitative spatio-temporal characterization of epileptic spikes using high density EEG: Differences between NREM sleep and REM sleep

Abstract

in this study, we applied high-density eeG recordings (HD-eeG) to quantitatively characterize the fine-grained spatiotemporal distribution of inter-ictal epileptiform discharges (IEDs) across different sleep stages. We quantified differences in spatial extent and duration of IEDs at the scalp and cortical levels using HD-eeG source-localization, during non-rapid eye movement (nReM) sleep and rapid eye movement (REM) sleep, in six medication-refractory focal epilepsy patients during epilepsy monitoring unit admission. Statistical analyses were performed at single subject level and group level across different sleep stages for duration and distribution of IEDs. Tests were corrected for multiple comparisons across all channels and time points. compared to nReM sleep, ieDs during ReM sleep were of significantly shorter duration and spatially more restricted. Compared to NREM sleep, IEDs location in ReM sleep also showed a higher concordance with electrographic ictal onset zone from scalp eeG recording. this study supports the localizing value of ReM ieDs over nReM ieDs and suggests that HD-eeG may be of clinical utility in epilepsy surgery work-up.

Can REM Sleep Localize the Epileptogenic Zone? A Systematic Review and Analysis

“…In Kang et al's recent report on spatial characteristics of REM vs. NREM IEDs, REM surface IEDs appeared to occupy new spatial territory relative to NREM IEDs in 4/6 patients ( 26 ). This assessment was made on our visual inspection of scalp IED fields in an original figure.…”

“…Kang et al ( 26 ) compared IEDs and clinical SOZs by the metric of lobar correspondence. Source reconstruction was performed on surface IEDs, yielding a probability density of possible cortical generators (see Figure 2 ).…”

“…Studies and methods were heterogeneous, so we will briefly describe them. Kang et al report a 53% reduction in scalp IED field size in REM compared to NREM, and, using source reconstruction techniques, a 24% size reduction in the spatial extent of probabilistic source generators ( 26 ). Okanari et al report that, amongst 20 patients with generalized IEDs yet non-lesional MRIs, REM lateralized the IED scalp field in 15 ( 28 ).…”

Local Sleep Slow-Wave Activity Colocalizes With the Ictal Symptomatogenic Zone in a Patient With Reflex Epilepsy: A High-Density EEG Study

“…REM sleep is a state characterized by EEG desynchronization, as demonstrated by decreased power in frequencies <30 Hz (Frauscher et al, 2016), probably mediated by cholinergic neurotransmission arising from subcortical inputs. This generalized tendency toward low voltage fast activity may favor the break-up of synchrony within epileptic networks (Shouse et al, 2000;Ng and Pavlova, 2013;Lambert et al, 2018;Kang et al, 2020). Overall, our results emphasize the importance of assessing local SWA across multiple vigilance states (i.e., comparing NREM sleep to REM sleep), suggesting that the opportunistic utilization of REM sleep SWA in the setting of epilepsy may assist to accentuate epilepsyinduced SWA maximums.…”

“…In neurological disease, focal SWA is a non-specific EEG finding, also occurring secondary to deafferentation in brain lesions caused by stroke or traumatic brain injury-in which case it may be independent of sleep-wakefulness processes (Dunkley et al, 2015;Rabiller et al, 2015;Rosanova et al, 2018). Given that REM sleep is thought to suppress epileptic activity (Shouse et al, 2000;Ng and Pavlova, 2013;Lambert et al, 2018;Kang et al, 2020), state-dependent SWA may more specifically localize epileptic foci, especially when comparing NREM sleep to REM sleep. This hypothesis is in line with our previous study where we reported no significant abnormality during REM sleep in patients' HDEEG topographies but noted increases in SWA during NREM sleep compared to REM sleep (Boly et al, 2017).…”