Primary hypersomnias of central origin

Hypersomnia is a frequently encountered symptom in clinical practice. The cardinal manifestation is inappropriate daytime sleepiness, common to all types of hypersomnias. Hypersomnias of central origin are a rare cause of excessive daytime sleepiness, much rarer than the hypersomnia related to other pathologies, such as sleep-disordered breathing. Narcolepsy, with or without cataplexy, remains the most well studied of the primary hypersomnias. Although recognized more than a century ago, it was not until the end of the 20th century that major breakthroughs led to a better understanding of the disease, with hope of more specific therapies. The authors review the major aspects of this disorder, including the newer treatment modalities. Idiopathic hypersomnia is also part of the primary hypersomnias. Although difficult to diagnose, certain peculiarities stand out to help us differentiate it from the more commonly seen narcolepsy. The recurrent hypersomnias, particularly the Kleine-Levin syndrome, will be discussed. This rare disorder has been studied more closely in the last few years with abundant epidemiologic data assembled through literature and worldwide case reviews. Understanding the primary central hypersomnias warrants a thorough look from the original description, as well as a peek at the future, while more efficacious diagnostic and therapeutic interventions are currently being developed.