Idiopathic Hypersomnia: Historical Account, Critical Review of Current Tests and Criteria, Diagnostic Evaluation in the Absence of Biological Markers and Robust Electrophysiological Diagnostic Criteria

Abstract

Idiopathic hypersomnia was first described in 1976 under two forms: polysymptomatic, characterized by excessive daytime sleepiness, long and unrefreshing naps, nocturnal sleep of abnormally long duration and signs of sleep drunkenness upon awakening; monosymptomatic, manifested by excessive daytime sleepiness only. Yet, after 45 years, this sleep disorder is still poorly delineated and diagnostic criteria produced by successive International Classifications of Sleep Disorders are far from satisfactory. The first part of this review is a historical account of the successive names and descriptions of idiopathic hypersomnia: monosymptomatic and polysymptomatic idiopathic hypersomnia in 1976; central nervous system idiopathic hypersomnia in 1979; idiopathic hypersomnia in 1990; idiopathic hypersomnia with and without long sleep time in 2005; idiopathic hypersomnia again in 2014; and, within the last few years, the proposal of separating idiopathic hypersomnia into a well-defined subtype, idiopathic hypersomnia with long sleep duration, and a more heterogeneous subtype combining idiopathic hypersomnia without long sleep duration and narcolepsy type 2. The second part is a critical review of both current ICSD-3 diagnostic criteria and clinical features, scales and questionnaires, electrophysiological and circadian control tests, research techniques, currently used to diagnose idiopathic hypersomnia. The third part proposes a diagnostic evaluation of idiopathic hypersomnia, in the absence of biologic markers and of robust electrophysiological diagnostic criteria.

Keywords:

• central disorders of hypersomnolence
• idiopathic hypersomnia
• idiopathic hypersomnia with long sleep time
• idiopathic hypersomnia without long sleep time
• idiopathic hypersomnia with long sleep duration
• idiopathic hypersomnia without long sleep duration
• narcolepsy
• narcolepsy type 1 and narcolepsy type 2

Abbreviations

CNS, central nervous system; CSF, cerebrospinal fluid; ESS, Epworth sleepiness scale; ICSD, International Classification of Sleep Disorders; IH, Idiopathic hypersomnia without affiliation status; IHwLST, idiopathic hypersomnia with long sleep time (from ICSD-2 to 2020); IHwoLST, idiopathic hypersomnia without long sleep time (from ICSD-2 to 2020); IHwLSD, idiopathic hypersomnia with long sleep duration (from 2020 on); IHwoLSD, idiopathic hypersomnia without long sleep duration (from 2020 on); MSLT, multiple sleep latency test; NT1, narcolepsy type 1 (from ICSD-3, 2014, on); NT2, narcolepsy type 2 (from ICSD-3, 2014, on); NwC, narcolepsy with cataplexy (from ICSD-2, 2005, to ICSD-3, 2014); NwoC, narcolepsy without cataplexy (from ICSD-2, 2005, to ICSD-3, 2014); PET, positron emission tomography; rCBF, regional cerebral blood flow; SOREMP, sleep onset REM period; SPECT, single photon emission computed tomography.

Credit Authorship Contribution Statement

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published, have agreed on the journal to which the article has been submitted, and agree to be accountable for all aspects of the work.

Disclosure

Dr Karel Sonka reports grants from Ministry of Health of the Czech Republic, during the conduct of the study. The authors declared no potential conflicts of interest with respect to authorship and/or publication of the article.

Additional information

Funding

Dr Sonka is supported by the grant from the Czech Ministry of Health AZV NU20-04-00088 touching idiopathic hypersomnia.