Current knowledge on the pathophysiology of idiopathic hypersomnia and potential mechanisms of action for low-sodium oxybate treatment.

Abstract

Study objectives: To elucidate hypotheses for the pathophysiology of idiopathic hypersomnia and discuss the mechanisms by which low-sodium oxybate (LXB) improves idiopathic hypersomnia symptoms.

Methods: Published literature on idiopathic hypersomnia sleep abnormalities, symptoms, treatments, and underlying pathophysiology was reviewed.

Results: Patients with idiopathic hypersomnia often show sleep architecture alterations, such as increased sleep efficiency and reduced slow-wave sleep, although the literature lacks consensus. The current understanding of pathophysiologic changes in idiopathic hypersomnia is sparse, but several hypotheses have been posited to explain specific symptoms. Long biological sleep clock, hypofunction of default mode network, dysregulated gamma-aminobutyric acid (GABA) signaling, inflammation, reduced physical activity, and immunologic abnormalities have been linked, to varying degrees, with the hallmark symptoms of idiopathic hypersomnia (excessive daytime sleepiness, sleep inertia, brain fog, dysautonomia). Treatment mechanisms may help elucidate pathophysiologic mechanisms. LXB effectively addresses idiopathic hypersomnia symptoms and is the only US-approved therapy for this indication. Oxybate, the active moiety in LXB, acts dose-dependently on GABA and gamma-hydroxybutyrate receptors, inhibits dopamine and noradrenaline signaling, and improves sleep architecture in people with narcolepsy. The effectiveness of LXB, a sleep-inducing treatment, on idiopathic hypersomnia symptoms suggests altered sleep architecture may contribute to this disorder.

Conclusions: Idiopathic hypersomnia, a sleep disorder with potentially debilitating symptoms, remains understudied. The underlying pathophysiology of idiopathic hypersomnia needs defining; insights can be gleaned from contextualizing current knowledge about mechanisms of effective treatments, such as LXB.