Abstract
SummaryOver the last two decades, our understanding of clinical and pathophysiological aspects of sleep‐related epileptic and non‐epileptic paroxysmal behaviours has improved considerably, although it is far from complete. Indeed, even if many core characteristics of sleep‐related hypermotor epilepsy and non‐rapid eye movement parasomnias have been clarified, some crucial points remain controversial, and the overlap of the behavioural patterns between these disorders represents a diagnostic challenge. In this work, we focused on segments of multichannel sleep electroencephalogram free from clinical episodes, from two groups of subjects affected by sleep‐related hypermotor epilepsy (N = 15) and non‐rapid eye movement parasomnias (N = 16), respectively. We examined sleep stages N2 and N3 of the first part of the night (cycles 1 and 2), and assessed the existence of differences in the periodic and aperiodic components of the electroencephalogram power spectra between the two groups, using the Fitting Oscillations & One Over f (FOOOF) toolbox. A significant difference in the gamma frequency band was found, with an increased relative power in sleep‐related hypermotor epilepsy subjects, during both N2 (p < .001) and N3 (p < .001), and a significant higher slope of the aperiodic component in non‐rapid eye movement parasomnias, compared with sleep‐related hypermotor epilepsy, during N3 (p = .012). We suggest that the relative power of the gamma band and the slope extracted from the aperiodic component of the electroencephalogram signal may be helpful to characterize differences between subjects affected by non‐rapid eye movement parasomnias and those affected by sleep‐related hypermotor epilepsy.
Highlights
Common during both childhood and adulthood, non-rapid eye movement (NREM) parasomnias are sleep disorders defined as abnormal behaviours arising typically from sleep stage N3, and occasionally from N2 (American Academy of Sleep Medicine, 2014)
All types of NREM parasomnias share some basic features: (i) the episodes arise in the first part of the night or of the sleep period; (ii) the subject is unresponsive to the environment during the episodes; (iii) there is post-episodic amnesia for events; (iv) electroencephalography (EEG) recordings show simultaneous sleep-like and wake-like features; (v) there are priming and precipitating factors
The dissociation between self-awareness and behaviour is a crucial feature of NREM parasomnias, and different studies have demonstrated a dissociation between wakefulness and sleep within different brain regions (Januszko et al, 2016; Sarasso et al, 2014; Terzaghi et al, 2009, 2012)
Summary
Common during both childhood and adulthood, non-rapid eye movement (NREM) parasomnias are sleep disorders defined as abnormal behaviours arising typically from sleep stage N3, and occasionally from N2 (American Academy of Sleep Medicine, 2014). Castelnovo et al (2016) demonstrated, with high-density EEG, the persistence of local sleep differences in SWA power during NREM and rapid eye movement (REM) sleep, and wakefulness, even during nights without clinical episodes, and they localized the local SWA decrease mainly to the cingulate and motor regions, supporting the theory that indicates the local arousals in these brain areas as the cause of NREM parasomnia motor behaviours (Terzaghi et al, 2012) These findings do not seem to make the process of diagnosis and differential diagnosis easier or quicker, and the gold-standard remains nocturnal video-polysomnography, an expensive, time-consuming and operator-dependent procedure, in which the video component is essential and, in association with the clinical features, allows to formulate the diagnosis by visual inspection. We chose to focus on sleep stages N2 and N3 because of the well-known peculiar association of both disorders with slow-wave sleep, with events arising typically from sleep stage N3 and, occasionally, from N2 (American Academy of Sleep Medicine, 2014)
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