Narcolepsy is a sleep disorder that occurs when the brain fails to regulate sleep-wake cycles. This can result in people falling asleep at inappropriate times, such as while working, having a conversation, and, most dangerously, while driving a car. Other characteristic symptoms include cataplexy (a sudden loss of voluntary muscle tone) and brief episodes of total paralysis at the beginning or end of sleep.
Narcolepsy is a chronic sleep disorder resulting from the brain's inability to regulate sleep-wake cycles. At various times throughout the day, people with narcolepsy experience the fleeting urge to sleep. If the urge becomes overwhelming, patients fall asleep for periods lasting from a few seconds to several minutes. In rare cases, some people may remain asleep for an hour or longer. There is no known cure for narcolepsy.
Although it is estimated that this condition afflicts as many as 200,000 Americans, fewer than 50,000 are diagnosed. It is as widespread as Parkinson's disease or multiple sclerosis (MS) and more prevalent than cystic fibrosis, but it is not as well known. Narcolepsy is often mistaken for depression, epilepsy, or the side effects of medications.
(Click People With Narcolepsy for more information on who is affected by this condition.)
Normally, when an individual is awake, brain waves show a regular rhythm. When a person first falls asleep, the brain waves become slower and less regular. This sleep state is called non-rapid eye movement (NREM) sleep. After about an hour and a half of NREM sleep, the brain waves begin to show a more active pattern again, even though the person is in deep sleep. This sleep state, called rapid eye movement (REM) sleep, is when dreaming occurs.
In narcolepsy, the order and length of NREM and REM sleep periods are disturbed, with REM sleep occurring at sleep onset instead of after a period of NREM sleep. Thus, narcolepsy is a disorder in which REM sleep appears at an abnormal time. Also, some of the aspects of REM sleep that normally occur only during sleep -- lack of muscle tone, sleep paralysis, and vivid dreams -- occur at other times in people with narcolepsy. For example, the lack of muscle tone can occur during wakefulness in a cataplexy episode. Sleep paralysis and vivid dreams can occur while falling asleep or waking up.