Differential diagnosis in hypersomnia.

Hypersomnia includes a group of disorders in which the primary complaint is excessive daytime sleepiness. Chronic hypersomnia is characterized by at least 3 months of excessive sleepiness prior to diagnosis and may affect 4% to 6% of the population. The severity of daytime sleepiness needs to be quantified by subjective scales (at least the Epworth sleepiness scale) and objective tests such as the multiple sleep latency test. Chronic hypersomnia does not correspond to an individual clinical entity but includes numerous different etiologies of hypersomnia as recently reported in the revised International Classification of Sleep Disorders. This review details most of those disorders, including narcolepsy with and without cataplexy, idiopathic hypersomnia with and without long sleep time, recurrent hypersomnia, behaviorally induced insufficient sleep syndrome, hypersomnia due to medical condition, hypersomnia due to drug or substance, hypersomnia not due to a substance or known physiologic condition, and also sleep-related disordered breathing and periodic leg movement disorders.