0657 THE CIRCADIAN VARIANT OF IDIOPATHIC HYPERSOMNIA

Abstract

Introduction: Idiopathic hypersomnia is a heterogeneous disorder, characterized by long sleep, excessive daytime sleepiness, absence of core narcolepsy features and normal orexin biology, and severe sleep inertia. Any contribution from circadian mechanisms is currently unknown. Methods: Patients presenting to the Beth Israel Deaconess Medical Center sleep center with clinical features suggesting idiopathic hypersomnia seen by the author were evaluated with a clinical examination and history, sleep logs, actigraphy, 24-hour urine 6-sulfatoxy melatonin (every 3 hours, in darkness, at home), and unrestricted polysomnography to capture the entire duration of sleep. Results: Fifty patients were evaluated in a 4 year period (2013- 2016). Mean age was 36.6 ± 8.4 years, mean ESS 16 ± 3, 35 were female, and BMI 27.3 ± 3.2 Kg/M2. Seasonal effects on mood were present in 12 patients; none demonstrated full criteria for seasonal affective disorder. Depression (27), fibromyalgia (16), circadian phase delay (7), hypertension (12) and sleep apnea (22) were main associations. MRI was performed and normal in 14. The biological night mean was 16 ± 1.2 hours, 10 were normal (not more than 9 hours). Subjective unconstrained total sleep time capability was 16 ± 2.1 hours, but habitual week day and weekend sleep was 9 ± 0.9 and 14 ± 2.1 hours, respectively. Polysomnographic total sleep time was 722 ± 32.2 minutes. If MSLTs were performed as per usual criteria, 26/50 could have received a diagnosis of narcolepsy without cataplexy, based on testing occurring in the biological night. Treatment responses with bright light therapy timed to the edges of the melatonin onset and baseline return were noted in the majority (32) of those with a long biological night, but not in those with a normal melatonin profile, with 32/40 continuing use for over 6 months. Sodium oxybate markedly improved two patients with a normal biological night and has not been effective so far in one patient with a long biological night. Conclusion: A subset of patients with idiopathic hypersomnia demonstrate a long biological night. 24-hour melatonin mapping can identify this phenotype, with implications for pathophysiology, diagnosis, and treatment of idiopathic hypersomnia.