Kleine-Levin syndrome

A rare neurological disease belonging to the group of disorders with central hypersomnolence. The same group also includes narcolepsy type 1 and 2 and idiopathic hypersomnia.

Diagnostic criteria
The disease is manifested by excessive daytime sleepiness (at least 2 episodes) lasting 2 days - 5 weeks. At least one episode per year or at least 18 months. The sufferer shows at least one of the following (during the episode): cognitive dysfunction, altered perception (derealization), eating disorder (anorexia or hyperphagia), disinhibited behavior (hypersexuality). Interestingly, between episodes the patient has normal alertness, cognitive function, behavior and mood are normal. K–L syndrome cannot be better explained by another sleep disorder, neurological, psychiatric (especially bipolar disorder) disease, medication or drugs.

Features of the disease
The disease usually begins in adolescence. Patients sleep up to 16-20 hours a day, they wake up (rather they are woken up) mostly only for food and hygiene. Patients tend to be apathetic, confused, exhausted, and speak slowly upon awakening (during an episode). Anterograde amnesia (for new information) is typical.

Etiology of the disease
The pathophysiology of the disease is unknown. Imaging methods show an abnormal finding in almost all patients – hypoperfusion (reduced blood supply) of the temporal and frontal lobes and the diencephalon (midbrain). These abnormalities are present during the episode but sometimes between episodes.

Familial occurrence of K–L syndrome was found in approximately five percent of cases. No psychiatric history was confirmed in the family of the patient with K–L syndrome.

Prevalence
Prevalence is estimated at 1–2/1,000,000. Around 500 cases have been diagnosed worldwide. The disease affects more men (2:1) than women.