7A21 Idiopathic hypersomnia

International Classification of Diseases for Mortality and Morbidity Statistics, 11th Revision, v2024-01

Idiopathic hypersomnia is characterised by daily periods of irrepressible need to sleep or daytime lapses into sleep occurring for at least several months in the absence of cataplexy or hypocretin deficiency (if determined). Polysomnography/multiple sleep latency test (MSLT) findings characteristic of narcolepsy (i.e., two or more sleep-onset REM periods (SOREMP’s), or one or more SOREMP’s on MSLT and a SOREMP on the preceding overnight polysomnography) should also be absent. The daytime sleepiness is not better explained by another disorder (e.g., insufficient sleep syndrome, obstructive sleep apnoea, circadian rhythm sleep-wake disorder), a substance or medication, or a medical condition). Objective evidence of hypersomnolence is indicated by an MSLT showing a mean sleep latency of ≤ 8 minutes or by polysomnography or wrist actigraphy showing a total 24-hour sleep time of 11 hours or more. Prolonged and severe sleep inertia is often observed and consists of sustained difficulty waking up with repeated returns to sleep, irritability, automatic behaviour, and confusion. In contrast to narcolepsy, naps are generally long, often more than 60 minutes, and unrefreshing. Note: A definitive diagnosis requires daily periods of irrepressible need to sleep or daytime lapses into sleep, objective demonstration of excessive sleepiness and absence of REM-related findings by multiple sleep latency test (MSLT/PSG).

synonyms

• Idiopathic hypersomnia
• disorder of excessive somnolence
• hypersomnia
• excessive somnolence

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