|Classification and external resources|
Idiopathic hypersomnia is a disease, thought to be a neurological disorder, which is characterized primarily by severe excessive daytime sleepiness (EDS). It has historically been rarely diagnosed and is often very difficult to diagnose
|Classification and external resources|
Idiopathic hypersomnia is a disease, thought to be a neurological disorder, which is characterized primarily by severe excessive daytime sleepiness (EDS). It has historically been rarely diagnosed and is often very difficult to diagnose at an early stage; it is usually a lifelong chronic disease, which is often debilitating. There is a very low level of public awareness of idiopathic hypersomnia, which often leads to stigma for those who suffer from it. Currently, there is no cure, there are no FDA-approved treatments, and research funding for its study is scarce.
In the medical literature, idiopathic hypersomnia may also be referred to as IH, IHS, primary hypersomnia, central hypersomnia, or hypersomnia of brain origin. The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) defines idiopathic hypersomnia as EDS without narcolepsy or the associated features of other sleep disorders. It occurs in the absence of medical problems that can cause secondary hypersomnia, and it occurs "despite normal quality and quantity of night time sleep (and sometimes despite exceptionally long periods of night time sleep). Primary Hypersomnia is thought to arise from problems with the brain’s systems that regulate sleep and wake."
- 1 Classification
- 2 Signs and symptoms
- 3 Causes
- 4 Diagnosis
- 5 Management
- 6 Prognosis
- 7 Epidemiology
- 8 Society and culture
- 9 Research
- 10 Support Groups
- 11 References
- 12 External links
In addition to differentiating between the primary and secondary hypersomnias, the 2001 International Classification of Sleep Disorders (ICSD) further classified the primary hypersomnia syndromes. These included idiopathic hypersomnia, narcolepsy, and the recurrent hypersomnias (like Klein-Levin syndrome).
The 2001 ICSD defines idiopathic hypersomnia as "a disorder of presumed central nervous system cause that is associated with a normal or prolonged major sleep episode and excessive sleepiness consisting of prolonged (1 to 2 hour) sleep episodes of N-REM"(non-rapid eye movement sleep). The ICSD initially described two clinical forms of idiopathic hypersomnia: "1) a polysymptomatic form with nocturnal sleep and naps of abnormally long duration with ‘sleep drunkenness’ on awakening, and 2) a monosymptomatic form manifested by isolated EDS." These forms were later described as idiopathic hypersomnia with long sleep time and idiopathic hypersomnia without long sleep time, respectively.
This classification has been steadily evolving, as further research has now shown overlap between narcolepsy and idiopathic hypersomnia. The 3rd edition of the ICSD is currently being finalized, and its new classification will label narcolepsy caused by hypocretin deficiency as “type 1 narcolepsy,” which is almost always associated with cataplexy. The other hypersomnias will remain subdivided based on the presence of sleep-onset rapid eye movement periods (SOREMPs). They will be labeled: “type 2 narcolepsy,” with 2 or more SOREMPs on mean sleep latency testing (MSLT); and “idiopathic hypersomnia,” with less than 2 SOREMPS.
However, “there is no evidence that the pathophysiology or therapeutic response is substantially different for hypersomnia with or without SOREMPs on the MSLT.” Given this currently understood overlap of idiopathic hypersomnia and narcolepsy, the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders has also updated its classification of the primary hypersomnias. It reclassified both idiopathic hypersomnia with and without long sleep time as major somnolence disorder (MSD). Additionally, MSD encompasses all syndromes of hypersomnolence not explained by low hypocretin, including not only idiopathic hypersomnia, but also narcolepsy without cataplexy, and long sleepers (patients requiring >10 hours sleep/day).
Further complicating these updated classification schemes, overlap between narcolepsy with cataplexy and idiopathic hypersomnia has also been reported. A subgroup of narcoleptics with long sleep time, comprising 18% of narcoleptics in one study, had symptoms of both narcolepsy with cataplexy and idiopathic hypersomnia (long sleep time and unrefreshing naps). It is felt that this subgroup might have dysfunction in multiple arousal systems. (See Causes section below).
Signs and symptoms
Those who suffer from idiopathic hypersomnia have recurring episodes of excessive daytime sleepiness (EDS). These occur in spite of “adequate, or more typically, extraordinary sleep amounts (e.g., greater than 10 hours per night).” Sleep is usually quite deep, with significant difficulty arousing from sleep, even with use of several alarm clocks. In fact, patients with IH often must develop elaborate rituals to wake, as alarm clocks and even physical attempts by friends/family to wake them may fail. Despite getting more hours of sleep than typically required by the human body, patients awake unrefreshed and may also suffer sleep inertia, known more descriptively in its severe form as sleep drunkenness (significant disorientation upon awakening). Daytime naps are generally very long (up to several hours) and are also unrefreshing, as opposed to the short refreshing naps associated with na