Sleep-related epileptic behaviors and non-REM-related parasomnias: Insights from stereo-EEG

Abstract

During the last decade, many clinical and pathophysiological aspects of sleep-related epileptic and non-epileptic paroxysmal behaviors have been clarified. Advances have been achieved in part through the use of intracerebral recording methods such as stereo-electroencephalography (S-EEG), which has allowed a unique "in vivo" neurophysiological insight into focal epilepsy. Using S-EEG, the local features of physiological and pathological EEG activity in different cortical and subcortical structures have been better defined during the entire sleep-wake spectrum. For example, S-EEG has contributed to clarify the semiology of sleep-related seizures as well as highlight the specific epileptogenic networks involved during ictal activity. Moreover, intracerebral EEG recordings derived from patients with epilepsy have been valuable to study sleep physiology and specific sleep disorders. The occasional co-occurrence of NREM-related parasomnias in epileptic patients undergoing S-EEG investigation has permitted the recordings of such events, highlighting the presence of local electrophysiological dissociated states and clarifying the underlying pathophysiological substrate of such NREM sleep disorders. Based on these recent advances, the authors review and summarize the current and relevant S-EEG literature on sleep-related hypermotor epilepsies and NREM-related parasomnias. Finally, novel data and future research hypothesis will be discussed.

EEG Functional Connectivity Prior to Sleepwalking: Evidence of Interplay Between Sleep and Wakefulness

“…In this sense, the localized coexistence of sleep and wake-like EEG activity observed in sleepwalkers may reflect a deregulation of an intrinsic property of the brain that can culminate in clinical episodes of somnambulism in predisposed individuals. 66 Relatedly, one study of pre-arousal EEG activity in adult sleepwalkers showed that increased SWA and slow oscillation density was specific to clinical episodes rather than generalized to all sleep-wake transitions. 17 It would thus be of interest to investigate the extent to which the patterns of EEG functional connectivity observed in the present study are specific to somnambulistic episodes.…”

Sleep‐related hypermotor epilepsy activated by rapid eye movement sleep

“…Video-EEG-PSG captured seven nocturnal seizures (four hypermotor and three PA), all occurring during REM sleep. However, some of these arousals may be surface-negative seizures which would be apparent upon stereoelectroencephalography (SEEG) (Gibbs et al, 2016). In our epilepsy and sleep disorder centre, this is the first case of SHE we have encountered which occurred during REM sleep.…”

Correlating Interictal Spikes with Sigma and Delta Dynamics during Non-Rapid-Eye-Movement-Sleep

“…However, these studies were conducted on scalp EEG, whereas we used intracranial EEG. This difference is important, as works using simultaneously extra- and intracranial recording have shown that only a fraction of IS are detected on the scalp (12, 13). The reason why IS seem to propagate better during deep sleep remains unclear.…”

“…Similarly, we defined the “spatial instability” as the standard variation of RDP across the different channels. The motivation for using this measure was the well-known fact that delta-sleep can be a local process (13–15). Here also, we found a positive correlation between instability and ISR.…”

“…Intracranial EEG is more accurate for the investigation of the relationship between sleep and epilepsy. First, because it allows the detection of interictal spikes (IS) that are not visible on the scalp (12, 13); second, because intracranial EEG offers a better spatial resolution highlighting the local behavior of both epileptic and physiological sleep activity (2, 13–15); finally, because the signal-to-noise ratio is higher in invasive than in non-invasive EEG (16). Recently, using Stero-EEG, it has been demonstrated that the suppressive effect of REM sleep on interictal epileptic activity is mainly observed during the occurrence of ocular movements [phasic REM sleep; (10, 11)], a phase characterized by significant reduction of synchronization at a local and global scale (11).…”