<prompt> True about narcolepsy:Sleep suddenPresents in Ilnd decadeCataplexyAll  <response>: A i.e. Sleep sudden; C i.e. Cataplexy; B i.e. Presents in IInd decadeNacrolepsyIt is a disorder most commonly present with uncontrollable sleep attacksQ in which patient abruptly falls asleep in inappropriate eg while eating, embarrassing eg during intercourse, and even dangerous eg while driving situations.Although sleep attacks have been described as brief eg. lasting 15-20 minutes and refreshing, this is not always true.The key features are?CataplexyQ sudden, brief episodes of paralysis with loss of muscle tone which occurs in most cases. Sleep paralysisQ brief paralysis associated with onset of sleep or wakefulnessHypnagogic hallucinationsQ dream like experience while falling asleep but not yet asleep.It usually begins in second decade 10-20 years Q i.e. adolescence occurs equally in males and females.The strong genetic association with HLA DR2, specifically HLA DQB1 602 85 suggests an autoimmune mechanism.In narcolepsy esp. with cataplexy, Hypocretins Orexins, the hypothalamic neuropeptide transmitter, regulating sleep-wake cycle, is decreased in brain and CSF along with the decrease in number of hypocretin-positive cells in hypothalamus.It results from defective REM sleep regulationQ. Sleep attacks hypnagogic hallucinations are dt REM intrusion, whereas cataplexy and sleep paralysis is atonia without REM.Diagnosis is confirmed by a sleep onset REM period on all night PSG or a positive MSLT in the sleep laboratory.Treatment includes:Stimulant drug eg. dexamfetamine to decrease sleepiness frequency of sleep attacks.- Modafinil, a non amfetamine stimulant to decrease day time sleepiness with less side effects. - Clomipramine other antidepressants to decrease cataplexy. 