Evaluation of Sleep Microstructure in Disorders of Arousal and Sleep-Related Hypermotor Epilepsy: Focus on Slow-Wave Sleep Fragmentation Analysis

Background: Disorders of Arousal (DOAs) and Sleep-Related Hypermotor Epilepsy (SHE) share overlapping clinical features, making their differential diagnosis challenging. While video-polysomnography remains the gold standard, microstructural distinctions between these conditions are not yet well defined. Notably, slow-wave sleep fragmentation has been established as a key marker of DOA, but its characteristics in SHE remain unexplored. Objective: This study aimed to investigate slow-wave sleep fragmentation in DOA and SHE, assessing its potential diagnostic value and exploring its dynamics across the night. Methods: Overnight polysomnography recordings were analyzed in adult and pediatric patients with DOA or SHE. Slow-wave sleep fragmentation was quantified, distinguishing between fast, mixed, and slow arousals, and evaluating its evolution across sleep cycles. Results: Slow-wave sleep fragmentation was significantly higher in DOA than in SHE, particularly in slow and mixed components, whereas SHE was characterized by a predominance of fast interruptions; moreover, patients with DOA exhibited a reduction in slow-wave sleep fragmentation in the later sleep cycles. Conclusion: These findings confirm greater slow-wave sleep instability in DOA compared to SHE and suggest that fragmentation patterns may serve as a novel diagnostic marker. The decrease in fragmentation in DOA may indicate a homeostatic modulation of arousal instability. Further research is needed to refine microstructural sleep parameters for improved diagnostic precision and targeted interventions.