Kleine-Levin Syndrome.

Kleine-Levin syndrome is a rare recurrent encephalopathy primarily affecting teenagers, characterized by relapsing-remitting episodes of hypersomnia along with cognitive, psychiatric and behavioral disturbances. During episodes, patients suddenly present hypersomnia (with sleep lasting 15-21 h/d), cognitive impairment (major apathy, confusion, slowness, amnesia), and a specific feeling of derealization (dreamy state, altered perception). Less frequently, they may also experience hyperphagia (66%), hypersexuality (53%, principally men), depressed mood (53%, principally women), anxiety, hallucinations, and acute brief psychosis (33%). Brain functional imaging is often abnormal. Stimulants are poorly beneficial during episodes, whereas lithium and valproate help reducing the episodes frequency and duration.