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narcolepsy Definition
Narcolepsy is a neurological disorder affecting the regulation of sleep. The person receives inappropriate messages from the brain regulating sleep and wake times.
What is going on in the body?
A person with narcolepsy has a lifelong sleep disorder. The central nervous system tells the body when to sleep and when to wake. In a person with narcolepsy, these messages are confused. The messages to sleep and wake happen at the wrong times. The body falls asleep when the person wants to be awake. The body can also be awake when the person wants to be sleeping.
What are the signs and symptoms of the condition?
Narcolepsy has four classic symptoms: - excessive daytime sleepiness. The person with narcolepsy will feel an irresistible urge to sleep during the day. This sleepiness can last from 30 seconds to 30 minutes. The person can feel these urges to sleep no matter how much sleep he or she has had the night before.
- sudden, short episodes of muscle weakness or paralysis, called cataplexy. The person usually feels paralysed or weak during times of strong emotion. Laughter, anger, surprise, anticipation, fear, or even a strenuous exercise workout can trigger the cataplexy.
- sleep paralysis. The paralysis can occur when a person is falling asleep or waking from sleep. Some people feel totally paralysed, while others experience partial paralysis.
- Vivid, sometimes frightening dreams that happen as a person is falling asleep. These dreams are called hypnagogic hallucinations.
Sometimes a person with narcolepsy will also have symptoms of disturbed nighttime sleep. He or she may toss and turn, jerk about, have nightmares, or wake up a lot.
The person may also have automatic behaviours. During the day, he or she may perform familiar and repetitive tasks without being fully aware of them, or remember them after they are finished.
The very first symptom to appear is usually the unrelenting, excessive sleepiness during the day. Someone with narcolepsy may have many symptoms or very few symptoms. The development of this disorder and the severity and frequency of the symptoms varies widely.
What are the causes and risks of the condition?
A recent study has shown that individuals with narcolepsy are missing cells from the hypothalamus that secrete a hormone called hypocretin, or orexin. On autopsy, the brains of people with narcolepsy showed clear evidence that the cells had been destroyed, perhaps by an autoimmune disorder or a toxin. An autoimmune disorder is one in which the person's body attacks its own tissues, for unknown reasons.
Since narcolepsy has been shown to run in families, there may be a genetic component to the condition. About 1 in 2,000 people have narcolepsy, and most of these have their first symptoms between the ages of 15 and 30.
What can be done to prevent the condition?
At this time, there is no way to prevent narcolepsy.
How is the condition diagnosed?
Diagnosis starts with a full family history. This is important because narcolepsy is often genetic. A physical examination is done to rule out any other causes of the symptoms. Finally, diagnosis is made after a visit to a sleep laboratory.
At the sleep laboratory: - Brain waves, body movements, and nerve and muscle function are observed, measured, and studied while the person is sleeping at night.
- A sleep study, known as a polysomnogram or PSG, is done to determine the degree of the person's excessive daytime sleepiness.
- A multiple sleep latency test is usually performed to measure the time it takes for the person to fall asleep and go into deep sleep. The test often is done while he or she takes naps and during nighttime sleeping. Most people fall asleep and then progress into REM or rapid eye movement sleep in about one and a half hours. A person with narcolepsy will fall into REM sleep right away.
If the diagnosis is uncertain, there is a genetic blood test that measures antigens found in people who often have narcolepsy. A positive result would support, but not prove, a diagnosis of narcolepsy.
What are the long-term effects of the condition?
Physically, the long-term effects are few. Most long-term effects are usually a result of the symptoms. For instance, an individual who falls asleep at the wrong times can be embarrassed and suffer social and economic consequences. The person may have trouble learning well in school, driving, or holding a job. Muscle weakness may interfere with physical activity. An individual may try to avoid strong emotions to lessen the symptoms. Finally, a person may become isolated, depressed, and lose touch with other people.
What are the risks to others?
A person with narcolepsy usually does not pose a risk to others, except when the excessive sleepiness occurs while driving a vehicle or operating dangerous machinery.
What are the treatments for the condition?
There are a number of treatments for narcolepsy that help manage the symptoms.
Excessive daytime sleepiness may be treated with stimulant medications. Ritalin has been used to control daytime sleepiness. Tricyclic antidepressants are used to treat muscle weakness and other symptoms. These medications can reduce symptoms, but usually will not alleviate them entirely.
It also helps if the person makes lifestyle changes. These can include: - creating a sleep schedule, with set times to go to bed, wake in the morning, and take short sleeps
- avoiding caffeinated foods and beverages in the evening
- exercising regularly, at least 3 hours before bed
- managing stress. A person with narcolepsy may benefit from learning how to keep stress to a minimum.
- joining support groups. Narcolepsy can be isolating. A person may benefit from being with other people who also have the condition.
- taking 10-minute sleeps 1 to 4 times a day. This can help a person function more normally.
What are the side effects of the treatments?
Side effects of the medications used to treat daytime sleepiness can include: Side effects of antidepressant medications can include drowsiness, erectile dysfunction, and low blood pressure.
Someone with narcolepsy who also has other health conditions, like high blood pressure, diabetes, or allergies, may find drug interactions that need to be carefully managed. All doctors need to be informed of all medications taken, including herbal remedies and over-the-counter medications.
What happens after treatment for the condition?
Treatment is monitored by a doctor, who will watch for side effects of medications, the onset of new diseases, and possible changes in symptoms.
How is the condition monitored?
A doctor watches how the person responds to medications and behavioural treatments.
Author: Terry Mason, MPH
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Contributors
Potential conflict of interest information for reviewers available on request |
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