Neuroimaging in Narcolepsy and Idiopathic Hypersomnia: from Neural Correlates to Clinical Practice

• Published in: Current sleep medicine reports Vol. 6; no. 4; pp. 251 - 266
• Main Authors: Gool, Jari K., Cross, Nathan, Fronczek, Rolf, Lammers, Gert Jan, van der Werf, Ysbrand D., Dang-Vu, Thien Thanh
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01-12-2020; Springer Nature B.V
• Subjects: Automation; Brain research; Cardiology; Family Medicine; General Practice; Hypersomnia Disorders (DT Plante; Hypothalamus; Internal Medicine; Magnetic resonance imaging; Medical imaging; Medicine; Medicine & Public Health; Neuroimaging; Neurology; Otorhinolaryngology; Patients; Psychiatry; Section Editor; Sleep disorders; Topical Collection on Hypersomnia Disorders; Neuroimaging; Idiopathic hypersomnia; Narcolepsy; Hypothalamus; Hypocretin
• ISSN: 2198-6401; 2198-6401
• DOI: 10.1007/s40675-020-00185-9

Purpose of Review
Clinical presentation of central hypersomnolence disorders, including narcolepsy type 1 and 2 and idiopathic hypersomnia, is often similar, and determining the correct diagnosis remains challenging. Neuroimaging techniques have provided valuable insights into the pathophysiology of narcolepsy and idiopathic hypersomnia. Here, we review current structural and functional brain imaging findings in central hypersomnolence disorders and discuss the future perspectives of neuroimaging in these sleep disorders.
Recent Findings
Most studies have focused on narcolepsy type 1 (or narcolepsy with cataplexy), showing inconsistent but extensive structural differences in the hypothalamus and its normally widespread projections. Functional studies have mainly focused on resting-state or emotion regulation in narcolepsy type 1 and have revealed disturbed activity in limbic and mesolimbic structures in relation to cataplexy. Finally, recent studies suggest a disruption of the default-mode network in patients with idiopathic hypersomnia.
Summary
Most neuroimaging studies to date have been conducted in small samples, while narcolepsy type 2 (or narcolepsy without cataplexy) and idiopathic hypersomnia remain relatively understudied. Larger studies with consistent clinical phenotyping should be the focus of future investigations. In addition, multi-modal imaging methods will be crucial to resolve previous inconsistencies and identify reliable objective biomarkers that could aid in understanding the pathophysiology and potentially support the diagnostic process.