Narcolepsy is a chronic neurological disorder involving the loss of the brain's ability to regulate sleep-wake cycles. Symptoms include excessive daytime sleepiness, comparable to how people who do not have narcolepsy feel after 24–48 hours of sleep deprivation, as well as disturbed sleep which often is confused with insomnia. 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 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. Those with narcolepsy generally experience the REM stage of sleep within five minutes of falling asleep, while people who do not 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.
It is most common between ages 40 and 50 and may decline after age 60. The term narcolepsy derives from the French wordnarcolepsie created by the French physician Jean-Baptiste-Édouard Gélineau by combining the Greek ????? (narke, "numbness" or "stupor"), and ????? (lepsis), "attack" or "seizure".
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http://www.hindawi.com/journals/sd/2014/271802/ lourdes m. delrosso, andrew l. chesson, and romy hoque, “manual characterization of sleep spindle index in patients with narcolepsy and idiopathic hypersomnia,” sleep disorders, vol. 2014, article id 271802, 4 pages, 2014. doi:10.1155/2014/271802
http://www.hindawi.com/journals/ije/2010/519607/ hermann l. müller, “increased daytime sleepiness in patients with childhood craniopharyngioma and hypothalamic tumor involvement: review of the literature and perspectives,” international journal of endocrinology, vol. 2010, article id 519607, 7 pages, 2010. doi:10.1155/2010/519607