Narcolepsy is a disorder that causes sudden episodes of deep sleep. These episodes can occur often and at inappropriate times, for example while a person is talking, eating or driving. Although sleep episodes can happen at any time, they may be more frequent during periods of inactivity or monotonous, repetitive activity.
Narcolepsy usually appears between ages 15 and 30, but the condition can appear earlier or later. Once it appears, narcolepsy is present for life. Men and women are affected equally.
About 60% of people with diagnosed narcolepsy have the combination of marked daytime sleepiness and sudden episodes of muscle weakness (called cataplexy). The muscle weakness can be so severe that a person with narcolepsy will collapse to the floor, but not become unconscious. This type of narcolepsy is associated with a shortage of a brain-stimulating protein called orexin (also known as hypocretin).
The cause of other types of narcolepsy is unknown. A genetic (inherited) predisposition appears to play a role.
People with narcolepsy don't require extra hours of sleep, but they do need daytime naps because they have difficulty staying awake for long periods. During the night, healthy people normally progress through several stages of sleep before entering or leaving the state of sleep called rapid eye movement (REM). During REM sleep, your brain waves resemble those of an awake person, visual dreams occur and muscle tone is slack. In narcolepsy, the brain-wave pattern can skip some or all of the other sleep stages, causing the person to move from the awake state immediately to REM sleep, or to awaken directly from the REM sleep stage.
The earliest symptom of narcolepsy is usually daytime sleepiness, which may be extreme. However, it may take years to recognize the disorder because other, more common causes of daytime sleepiness often are blamed for the symptoms.
Narcolepsy has four main symptoms. It is common for people with narcolepsy to have more than one symptom, but it is rare for a person with the disease to experience all four:
- Excessive daytime sleepiness. This is always present and is usually the most prominent symptom.
- Cataplexy. This is the sudden, temporary loss of muscle tone, which causes paralysis of the head or body while the person remains conscious. It can last a few seconds or several minutes. Mild attacks can cause slurred or stuttering speech, drooping eyelids or hand weakness that causes the person to drop objects. Severe attacks can cause the knees to buckle, leading to collapse. Typically, cataplexy is brought on by laughter, excitement or anger. The sudden relaxing of muscle tone is probably the result of the brain abruptly entering REM sleep.
- Sleep paralysis. This is the temporary inability to move while falling asleep or awakening. It lasts no more than several minutes. Like cataplexy, sleep paralysis probably is related to insufficient separation between REM sleep and the awake state.
- Hypnagogic hallucinations. These are dreamlike images that are seen during the awake state instead of during sleep. These often-frightening visions are seen just as the person is falling asleep or waking up. They tend to occur in people who also have sleep paralysis.
Symptoms usually begin during adolescence or young adulthood. People with narcolepsy complain of fatigue, experience impaired performance at work and school, and may have difficulty in social relationships. Excessive daytime sleepiness can be disabling and may greatly diminish a person's quality of life. Memory lapses and visual disturbances may be particularly upsetting.
More than 50% of people with narcolepsy experience periods of memory lapse or blackouts caused by very short periods of sleep called micro-sleeps. Micro-sleeps are not unique to people with narcolepsy, and they can be experienced by anyone who is severely sleep deprived. They are periods of sleep that last only a few seconds, and usually are not noticed. During such episodes, a person may get lost while walking or driving, write or speak nonsense, misplace objects, or bump into things. Later in the course of narcolepsy, a person also can develop insomnia (difficulty sleeping) during normal sleeping hours.
To diagnose narcolepsy, your doctor will ask you about your history of typical episodes and will have you undergo an overnight sleep study. The sleep study checks for other explanations that could account for daytime sleepiness, such as sleep apnea or other causes of sleep interruptions. The sleep test measures brain waves, eye movements, muscle activity, heartbeat, blood oxygen levels and breathing.
A specific study called a multiple sleep latency test is a necessary part of the evaluation for narcolepsy. This test must be done after the person has had an adequate night's sleep. A multiple sleep latency test consists of four 20-minute opportunities to nap, which are offered every two hours throughout the day. Patients with narcolepsy fall asleep in approximately five minutes or less, and move into REM sleep during at least two of the four naps. Normal well-rested sleepers take about 12 to 14 minutes to fall asleep for a daytime nap, and don't fall directly into REM sleep.
Narcolepsy cannot be cured and does not go away. In most cases, symptoms can be diminished with medications, regularly scheduled naps and good sleep habits.
There is no way to prevent narcolepsy. For people who have the condition, avoiding conditions that bring on narcolepsy episodes may help to reduce their frequency. If you have narcolepsy and your symptoms are not controlled with medicines, you should never smoke because you could fall asleep with a lit cigarette, and you should never drive.
The main symptom of narcolepsy, excessive daytime sleepiness, can be partially relieved with stimulants such as modafinil (Provigil), armodafinil (Nuvigil) methylphenidate (Ritalin and other brand names) or dextroamphetamine (Dexedrine), as well as with regularly scheduled short naps during the day.
Cataplexy and sleep paralysis can be treated with a variety of medicines that can make you more resistant to entering REM sleep. Most of these medicines were developed for use as antidepressants. Examples of potentially effective medications include protriptyline (Vivactil), venlafaxine (Effexor) and fluoxetine (Prozac).
Cataplexy also can be treated with sodium oxybate (also called gamma hydroxybutyrate or Xyrem), although the use of this drug is tightly controlled because it has been abused recreationally. For reasons that are not well understood, a low dose of this medicine reduces cataplexy attacks and improves daytime sleepiness in people who have narcolepsy with cataplexy, even though the drug causes sedation in most people without narcolepsy.
Psychological counseling may be important for difficulties associated with self-esteem and for emotional support, especially since people with narcolepsy have difficulty doing tasks that require concentration, and may be regarded as unmotivated by family and peers.
Call a doctor if you are excessively sleepy during the day. You should be evaluated as quickly as possible if episodes occur while you are driving a car or operating machinery.
People with narcolepsy have a significantly higher risk of death or serious injury resulting from motor vehicle or job-related accidents, and they must take care to avoid situations where such accidents might occur.
National Center on Sleep Disorders Research
National Institutes of Health
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National Institute of Neurological Disorders and Stroke
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