Idiopathic hypersomnia

Idiopathic hypersomnia
Classification and external resources
Specialty	Neurology
ICD-10	G47.11, G47.12
ICD-9-CM	327.11, 327.12
MedlinePlus	000803
eMedicine	med/3129
MeSH	D020177
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Idiopathic hypersomnia is a condition, thought to be a neurological disorder, which is characterized primarily by 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. There is currently no cure, but there are several off-label treatments, which are primarily FDA-approved narcolepsy medications. 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 or sleep disruptions, such as sleep apnea, that can cause secondary hypersomnia, and is therefore considered a subset of the primary hypersomnias, which 'are thought to arise from problems with the brain’s systems that regulate sleep and wake.'

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.

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