hypersomnias

Hypersomnias are a group of sleep disorders characterized by excessive daytime sleepiness, long or frequent daytime sleep episodes, or both, not explained by inadequate sleep, misaligned circadian rhythm, or another medical or psychiatric condition. They can be classified as primary (intrinsic sleep disorders) or secondary (sleepiness arising from another condition or factor).

The major primary hypersomnias include narcolepsy, idiopathic hypersomnia, and Klein-Levin syndrome. Narcolepsy typically presents with sudden sleep attacks, excessive daytime sleepiness, and often abrupt muscle weakness (cataplexy) triggered by strong emotions. Narcolepsy type 1 is usually associated with low or absent hypocretin (orexin) in the cerebrospinal fluid; type 2 lacks cataplexy and hypocretin deficiency. Idiopathic hypersomnia is characterized by persistent sleepiness with prolonged nocturnal sleep and sometimes long naps, without the sleep-onset REM features that distinguish narcolepsy. Klein-Levin syndrome involves recurrent episodes of hypersomnia lasting days to weeks, often with behavioral changes and cognitive disturbances, primarily in adolescence.

Secondary hypersomnias arise from other conditions that disrupt sleep or promote sleepiness, such as obstructive sleep apnea, insufficient sleep, certain medications, neurological or metabolic disorders, or mood disorders. A comprehensive assessment distinguishes hypersomnias from sleep deprivation, circadian rhythm disorders, and other sleep disorders.

Diagnosis relies on clinical history corroborated by sleep studies. Overnight polysomnography rules out other sleep disorders, and multiple sleep latency testing helps differentiate narcolepsy from other hypersomnias. Treatment is individualized and may include scheduled daytime naps, wake-promoting medications (for example, modafinil, armodafinil, solriamfetol, or pitolisant), and, in narcolepsy with cataplexy, sodium oxybate or certain antidepressants. Managing any underlying conditions is also important.