Résumé
Chronic hypersomnias correspond to numerous etiologies of patients with a complaint of excessive daytime sleepiness and affect 4% to 6% of the general population. Hypersomnia significantly interferes with several aspects of life, with negative social and professional impacts. Several steps of evaluation of these patients are required to explore sleep and sleepiness, to quantify the severity of the condition, and to achieve a diagnosis of chronic hypersomnia. Hence, clinical interviews, questionnaires, sleep diaries, polysomnography, the Multiple Sleep Latency Test, the Maintenance of Wakefulness Test, and additional tests in particular circumstances (measurement of hypocretin-1 in cerebrospinal fluid, the presence of the HLA DQB1*0602 genotype, and brain computed tomography (CT) scan and/or magnetic resonance imaging (MRI)) allow us to assess the definitive diagnosis of hypersomnia. We will detail in this chapter the clinical signs, laboratory investigations, pathophysiology, and the management of most etiologies of chronic hypersomnia as reported in the revised International Classification of Sleep Disorders, 2nd Edition—ICSD-II: narcolepsy with and without cataplexy; idiopathic hypersomnia with and without long sleep time; recurrent hypersomnia; behaviorally induced insufficient sleep syndrome; and hypersomnia due to medical, neurological, and psychiatric disorders and/or drug or substance use.