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Narcolepsy is a chronic neurological disorder involving the loss of the brain's ability to regulate sleep-wake cycles normally. People with narcolepsy experience excessive daytime sleepiness, comparable to how people who don't have narcolepsy feel after 24–48 hours of sleep deprivation,〔(【引用サイトリンク】title =What is Narcolepsy? )〕 as well as disturbed nocturnal sleep which often is confused with insomnia. Those with narcolepsy generally experience the REM stage of sleep within 5 minutes of falling asleep, while people who don't have narcolepsy (unless they are significantly sleep deprived) do not experience REM until after a period of slow-wave sleep, which lasts for about the first hour or so of a sleep cycle. Another common symptom of narcolepsy is cataplexy, a sudden and transient episode of muscle weakness accompanied by full conscious awareness, typically (though not necessarily) triggered by emotions such as laughing, crying, terror, etc. affecting roughly 70% of people who have narcolepsy. The system which regulates sleep, arousal, and transitions between these states in humans is composed of three interconnected subsystems: the orexin projections from the lateral hypothalamus, the reticular activating system, and the ventrolateral preoptic nucleus.〔 In narcoleptic individuals, these systems are all associated with functional impairments due to a greatly reduced number of hypothalamic orexin projection neurons and significantly fewer orexin neuropeptides in cerebrospinal fluid and neural tissue, compared to non-narcoleptic individuals. The term ''narcolepsy'' derives from the French word ''narcolepsie'' created by the French physician Jean-Baptiste-Édouard Gélineau by combining the Greek νάρκη (''narkē'', "numbness" or "stupor"),〔Entry (Narcolepsy. ) in the Online Etymology Dictionary. Douglas Harper, Historian. 18 September 2007.〕 and λῆψις (''lepsis''), "attack" or "seizure". ==Classification== The 2001 International Classification of Sleep Disorders (ICSD) divides primary hypersomnia syndromes between narcolepsy, idiopathic hypersomnia, and the recurrent hypersomnias (like Klein-Levin syndrome); it further divides narcolepsy into that with cataplexy and that without cataplexy.〔(【引用サイトリンク】title=About Hypersomnia )〕 This ICSD version defines narcolepsy as “a disorder of unknown etiology that is characterized by excessive sleepiness that typically is associated with cataplexy and other REM-sleep phenomena, such as sleep paralysis and hypnagogic hallucinations". It also establishes baseline categorical standards for diagnosis of narcolepsy, through 2 sets of well defined criteria, as follows. Minimal narcolepsy diagnostic criteria set #2: *A "complaint of excessive sleepiness or sudden muscle weakness." *Associated features that include: sleep paralysis; disrupted major sleep episode; hypnagogic hallucinations; automatic behaviors. *Polysomnography with one or more of the following: "sleep latency less than 10 minutes;" "REM sleep latency less than 20 minutes;" an MSLT with a mean sleep latency less than 5 minutes; "two or more sleep-onset REM periods" (SOREMPs). *”No medical or mental disorder accounts for the symptoms.” (see hypersomnia differential diagnosis)〔 In the absence of clear cataplexy, it becomes much more difficult to make a firm diagnosis of narcolepsy. “Various terms, such as essential hypersomnia, primary hypersomnia, ambiguous narcolepsy, atypical narcolepsy, etc., have been used to classify these patients, who may be in the developing phase of narcolepsy.” 〔 Since the 2001 ICSD, the classification of primary hypersomnias has been steadily evolving, as further research has shown more 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 primary hypersomnias will remain subdivided based on the presence of SOREMPs. They will be labeled: “type 2 narcolepsy,” with 2 or more SOREMPs on 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 (DSM-V) is also updating its classification of the primary hypersomnias. It reclassifies narcolepsy without cataplexy as major somnolence disorder (MSD). Additionally, MSD will encompass all syndromes of hypersomnolence not explained by low hypocretin, including idiopathic hypersomnia (with and without long sleep time) and long sleepers (patients requiring >10 hours sleep/day).〔〔(【引用サイトリンク】 Diagnosis of Idiopathic Hypersomnia/ Major Hypersomnolence Disorder )〕 Further complicating these updated classification, 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, including hypocretin and GABA (see idiopathic hypersomnia causes). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「narcolepsy」の詳細全文を読む スポンサード リンク
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