Sleep disturbances in SCN8A‐related disorders

Objectives: People with neurodevelopmental disorders frequently experience sleep disturbances, negatively impairing their quality of life. We aimed to determine the prevalence and nature of sleep disturbances in patients with SCN8A-related disorders. Methods: Through a collaborative network of caregivers and clinicians, we collected data about epilepsy, cognitive/motor abilities, medications, and relevant comorbidities of patients harboring a pathogenic SCN8A variant. The Sleep Disturbance Scale for Children (SDSC), the Children's Sleep Habits Questionnaire (CSHQ-22-items), and the Pediatric Daytime Sleepiness Scale (PDSS) were distributed and evaluated by factor scores and Composite Sleep Index. Video-EEG-polysomnographic recordings were performed. Results: We enrolled 47 patients (age range: 2-39 years), whose phenotypes ranged from SCN8A-DEE to intellectual disability without epilepsy. In the majority of them (82%), sleep disturbances were reported and/or observed at the SDSC. The most frequent were difficulty in initiating and maintaining sleep (64%), followed by sleep breathing disorder (43%), sleep-wake transition disorder (34%), and daytime sleepiness (34%). Sleep disturbances were more frequent in patients with severe DEE (96%) and ongoing seizures (93%) and were more severe in patients with sleep-related seizures. The CSHQ and PDSS confirmed difficulty in initiating and maintaining sleep. Polysomnographic recordings (9 patients/20 nights) showed an altered sleep structure in 95%, with frequent arousals, mainly not seizure related. Significance: More than 80% of patients with SCN8A-related disorders presented with sleep disturbances, primarily consisting of sleep instability with difficulty of initiating and maintaining sleep. Animal studies showed sleep disturbances in SCN8A- and SCN1A-Dravet Syndrome mice models, suggesting a role for voltage-gated sodium channels in the regulation of sleep. Understanding the effects of SCN8A dysfunction on sleep stability may guide future therapeutic efforts to alleviate this often distressing symptom also in seizure-free SCN8A patients.