Idiopathic hypersomnia (IH) is a chronic central hypersomnolence disorder that impairs daily functioning and quality of life. Lacking definitive biomarkers, IH is frequently misdiagnosed or mistaken for psychiatric conditions. Diagnostic challenges include the limited specificity of the multiple sleep latency test (MSLT) in distinguishing IH from narcolepsy type 2 (NT2). Accurate diagnosis requires exclusion of other causes and objective evaluation with actigraphy or extended polysomnography (PSG). Evidence of GABAergic dysfunction suggests potential biomarkers. Low-sodium oxybate improves sleepiness and inertia. This review summarizes current knowledge of IH pathophysiology, highlights key diagnostic considerations, and provides an evidence-based overview of therapeutic approaches and future research directions aimed at improving individualized care.

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