Disorders of excessive sleepiness: narcolepsy and hypersomnia.

Besides sleep apnea, the main disorders of excessive daytime sleepiness include narcolepsy and hypersomnia. Narcolepsy is characterized by periods of irresistible sleepiness and sleep attacks of brief duration and, most often, by one or more of the auxiliary symptoms: cataplexy, sleep paralysis, and hypnogogic hallucinations. Generally, sleepiness and sleep attacks in hypersomnia are of longer duration and are more resistible than in narcolepsy; also, the auxiliary symptoms are absent. There are three types of hypersomnia: idiopathic, secondary, and periodic. Nocturnal sleep is typically disrupted in narcolepsy, whereas in idiopathic hypersomnia it is prolonged and in secondary hypersomnia it is variable. The exact causes of narcolepsy and idiopathic hypersomnia are unknown; however, there is evidence for genetic predisposition for either disorder. In secondary hypersomnia causative factors include: neurologic, such as head injuries, cerebrovascular insufficiency, and brain tumors; general medical, such as metabolic disorders, various intoxications, and conditions leading to brain hypoxia; and psychiatric, most notably depression. Although the cause of periodic hypersomnia is unclear, most research supports the notion of underlying organic disease. Often, the evaluation of patients with excessive daytime sleepiness can be completed in the office setting, based on the sleep history and a thorough neurologic, general medical, and psychiatric assessment. Whenever indicated, ancillary laboratory studies, such as computed tomography and magnetic resonance scans, should be performed. Sleep laboratory recordings generally are not necessary unless there is suspicion of sleep apnea or narcolepsy in the absence of auxiliary symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)