Narcolepsy Health Article

Definition

Narcolepsy is a disorder of the nervous system marked by excessive daytime sleepiness, uncontrollable sleep attacks, and cataplexy (a sudden loss of muscle tone, usually lasting up to half an hour). The American Psychiatric Association (APA) classifies narcolepsy as a sleep disorder in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders, or DSM-IV. The National Institute of Neurological Disorders and Stroke (NINDS) defines narcolepsy as a "disorder caused by the brain's inability to regulate sleep-wake cycles normally." The disorder is sometimes called Gélineau's syndrome because it was first identified in 1880 by the French neurologist Jean-Baptiste Gélineau. The word narcolepsy itself comes from two Greek words that together mean "seized by sleepiness."

Description

Narcolepsy is the second-leading cause of excessive daytime sleepiness (after obstructive sleep apnea). Persistent sleepiness and sleep attacks are the hallmarks of this condition. The sleepiness has been compared to the feeling of trying to stay awake after not sleeping for two or three days. It is not correct, however, to describe people with narcolepsy as sleeping longer or spending more time asleep in a 24-hour period than people without the disorder. Although patients with narcolepsy experience drowsiness and sleep attacks during the daytime, they also wake up frequently during the nighttime hours. For this reason, narcolepsy is more accurately described as a disorder of the normal boundaries between sleep and wakefulness.

People with narcolepsy fall asleep suddenly—anywhere, at any time, maybe even in the middle of a conversation. These sleep attacks can last from a few seconds to more than an hour. Depending on where they occur, they may be mildly inconvenient or even dangerous. Some people continue to function outwardly during the sleep episodes, such as talking or putting things away. But when they wake up, they have no memory of the event.

Narcolepsy is related to the deep, dreaming part of sleep known as rapid eye movement (REM) sleep. Normally when people fall asleep, they experience 80 to 100 minutes of non-REM sleep, which is then followed by about 20 minutes of REM sleep. People with narcolepsy, however, enter REM sleep immediately. In addition, REM sleep occurs inappropriately throughout the day in patients with narcolepsy.