Kleine-Levin syndrome.

Kleine-Levin syndrome, sometimes referred to as Rip van Winkle disease, is a rare sleep disorder mainly affecting teenage boys in which the main features are intermittent hypersomnolence, behavioural and cognitive disturbances, hyperphagia and in some cases hypersexuality. Each episode lasts for one or two weeks, and affected people are entirely asymptomatic between episodes. No definite cause has been identified but hypothalamic dysfunction seems likely. Relapses may occur every few weeks or months, and the condition may last for a decade or more before spontaneous resolution. There is no effective treatment but stimulants such as methylphenidate and modafinil as well as the mood stabiliser lithium carbonate have been tried with varying success.