In a paper published this month in Neurology, the Idiopathic Hypersomnia Severity Scale (IHSS), a brief self-report instrument designed to measure the severity of the key symptoms of idiopathic hypersomnia (IH), was validated. If much is known in the field of narcolepsy, IH remains largely unknown. This central hypersomnia is characterized by severe excessive daytime sleepiness (EDS), prolonged nighttime sleep, and sleep inertia (i.e. difficulty in awakening from sleep, in the morning and after naps). EDS, the most common symptom, often occurs also in the general population with various phenotypes; and psychometric tools, as the widely used Epworth Sleepiness Scale, were developed to evaluate its severity. However, a specific instrument to assess the spectrum of IH symptoms was lacking so far.

IHSS is a 14-item self-administered questionnaire that assesses nighttime sleep symptoms and the related sleep inertia (5 items), daytime sleep symptoms and the related sleep inertia (4 items), and impaired daytime functioning due to hypersomnolence (5 items). All items are scored from 0 to 3 or 4, depending on severity, that provide a score, ranging from 0 to 50, with the highest score reflecting more severe and frequent symptoms. The psychometric properties, discriminant diagnostic validity, and score changes with treatment of the scale were assessed, after being administered to 210 participants from the French National Reference Center for central Hypersomnia. IHSS turned out to be a reliable and valid clinical tool for the quantification of IH symptoms and consequences. This questionnaire will be useful for future research for patients identification, follow-up, and management.

The Idiopathic Hypersomnia Severity Scale (IHSS) has been developed and is copyrighted by Professor Yves Dauvilliers. IHSS © Yves Dauvilliers, 2018. The IHSS is distributed worldwide by Mapi Research Trust, a not for profit organization, based in France. For any further information on the utilization of the IHSS, please contact Mapi Research Trust at:

https://eprovide.mapi-trust.org/instruments/idiopathic-hypersomnia-severity-scale

Y. Dauvilliers, E. Evangelista, L. Barateau, R. Lopez, S. Chenini, C. Delbos, S. Beziat, I. Jaussent. Measurement of symptoms in idiopathic hypersomnia. The Idiopathic Hypersomnia Severity Scale. Neurology. 2019 Apr 9;92(15):e1754-e1762. doi: 10.1212/WNL.0000000000007264. Epub 2019 Mar 13. https://www.ncbi.nlm.nih.gov/pubmed/30867266