Moreover, life‐threatening accidents may occur, for instance while driving ( Findley 1995 George 1996). There is evidence that symptoms of narcolepsy may adversely affect people's quality of life, having a major impact upon education, recreation and occupation, with impaired learning, work performance, promotion and earnings ( Beusterien 1999 Broughton 1981 Broughton 1983 Daniels 2001 Ervik 2006 Goswami 1998 Kales 1982 Teixeira 2004 Vignatelli 2004). According to current international diagnostic criteria ( AASM 2005) the diagnosis of narcolepsy without cataplexy is confirmed only by multiple sleep latency tests (mean sleep latency less than eight minutes and two or more sleep‐onset REM periods). When excessive daytime sleepiness is present without cataplexy (narcolepsy without cataplexy subtype) the diagnosis, according to previous international diagnostic criteria ( AASM 2001), is confirmed if there are specific findings during nocturnal polysomnography (sleep latency less than 10 minutes and REM sleep latency less than 20 minutes) and multiple sleep latency test (mean sleep latency less than five minutes and two or more sleep‐onset REM periods). Current international diagnostic criteria ( AASM 2005) states that together with the above reported two symptoms diagnosis "should be confirmed" by multiple sleep latency test (mean sleep latency less than or equal to eight minutes and two or more more sleep‐onset REM periods) or alternatively by hypocretin‐1 levels in cerebrospinal fluid (less than or equal to 110 pg/mL). Previous international diagnostic criteria ( AASM 2001) deems the combination of excessive daytime sleepiness and cataplexy (narcolepsy with cataplexy subtype: about 80% of cases) as sufficient for a definite diagnosis. Disturbed nocturnal sleep and other sleep symptoms are also reported to affect people with narcolepsy. This includes cataplexy, sleep paralysis (inability to move during the transition from sleep to wakefulness), and hypnic hallucinations (hallucinations that occur during sleep‐wake transition). Other manifestations are the abnormal appearance of REM sleep features during the wake or sleep‐wake transition states. The main symptom, always present, is excessive daytime sleepiness, principally occurring as daily episodes of unwanted sleep. The course is usually stable, sometimes with remissions or exacerbations. The age at diagnosis has a mean delay of more than 10 years because of the frequent misdiagnosis with other neurological or psychiatric conditions ( Dauvilliers 2001). The age at onset is between early childhood and mid adulthood the peak is in the second decade ( Guilleminault 2000 Silber 2002). An autoimmune mechanism of damage has been hypothesized ( Dauvilliers 2007 Mignot 2001). The pathogenic cause is purported to be the dysfunction or destruction of a group of hypothalamic neurones transmitting the neurotransmitter hypocretin (also called orexin) ( Mignot 2000). Narcolepsy is a disorder of brain mechanisms governing the sleep‐wake cycle. Estimates of the prevalence of narcolepsy range between the extremes of 0.23 and 590 cases per 100,000 (Israel and Japan respectively) in Caucasian ethnic groups there are about 20 to 60 cases per 100,000 ( Partinen 2000). Cataplexy causes an abrupt and transient decrease or loss of muscle tone, affecting the limbs bilaterally, or the trunk or both, and is elicited by emotional stimuli ( Guilleminault 2000). Narcolepsy is a lifelong disorder of the central nervous system characterized by uncontrollable daytime sleepiness (also called "excessive daytime sleepiness") and intermittent abnormal manifestations of rapid eye movement (REM) sleep during wake or sleep‐wake transition, of which cataplexy is the most prominent. This review is an update of a previously published review in The Cochrane Database of Systematic Reviews (Issue 1, 2008) on 'Antidepressant drugs for narcolepsy'.
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