Narcolepsy is a chronic sleep disorder that causes excessive, overwhelming daytime sleepiness.
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.
Narcolepsy has four classic symptoms: cataplexy. Cataplexy involves sudden, short episodes of muscle weakness or paralysis. The person usually feels paralyzed or weak during times of strong emotion. Laughter, anger, surprise, anticipation, fear, or even a strenuous exercise workout can trigger the cataplexy.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.hypnagogic hallucinations. These involve vivid, sometimes frightening dreams that happen as a person is falling asleep.sleep paralysis. The paralysis can occur when a person is falling asleep or awakening from sleep. Some people feel totally paralyzed, while others experience partial paralysis.
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 behaviors. During the day, he or she may perform familiar and repetitive tasks without being fully aware of them. The person may not remember this behavior afterwards.
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 vary widely.
The cause of narcolepsy is still being figured out by researchers. 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. A group of genes on chromosome 6 have been found to have some association with narcolepsy. However, it is not inherited in an autosomal recessive, X-linked, or any other classic pattern. About 1 in 2,000 people has narcolepsy, and most of these have their first symptoms between the ages of 15 and 30.
At this time, there is no way to prevent narcolepsy.
Diagnosis of narcolepsy starts with a full family medical 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 (PSG) is done to determine the degree of the person's excessive daytime sleepiness.A multiple sleep latency test (MSLT) is usually performed. This test measures the time it takes for the person to fall asleep and go into deep sleep. The test is often done during naps and nighttime sleep. Most people progress into REM or rapid eye movement sleep in about 1-1/2 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.
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 and depressed.
Narcolepsy is not contagious and poses no risk to others. It does, however, have a genetic component.
There are a number of treatments for narcolepsy that help manage the symptoms.
Excessive daytime sleepiness may be treated with medicines that stimulate the central nervous system. These stimulants include: dextroamphetamine sulfate (i.e., Dexedrine)methylphenidate (i.e., Metadate, Ritalin, Concerta, Methylin)pemoline (i.e., Cylert)modafinil (i.e., Provigil)
Tricyclic antidepressants are used to treat muscle weakness and other symptoms. These medicines can reduce symptoms but usually will not alleviate them entirely. Amitriptyline (i.e., Elavil) and nortriptyline (i.e., Pamelor, Aventyl) are commonly prescribed tricyclic antidepressants.
It also helps if the person makes lifestyle changes. These can include: avoiding caffeinated foods and beverages in the eveningcreating a sleep schedule, with set times to go to bed, wake in the morning, and take napsexercising regularly, at least 3 hours before bedjoining support groupsmanaging stresstaking 10-minute naps one to four times a day
Side effects of central nervous system stimulants include: addiction to the medicinearrhythmia, or irregular heartbeatheadacheinsomnianervousness and irritabilitymood changes
Antidepressants can cause drowsiness, erectile dysfunction, and low blood pressure.
Treatment of narcolepsy is lifelong.
The person with narcolepsy needs to make regular visits with the healthcare professional, to whom any new or worsening symptoms should be reported.
National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
Living With Narcolepsy, National Sleep Foundation, 1522 K Street NW, Suite 500, Washington, DC 20005
Narcolepsy, Questions and Answers, Narcolepsy Network, 10921 Reed Hartman Highway, Cincinnati, OH 45242
Mayo Clinic Family Health Book, David E. Larson, 1996