An extreme tendency towards excessive sleepiness often associated with cataplexy, in which sleep onset is accompanied by dreaming. Sleep paralysis and hypnagogic (during the process of falling asleep) hallucinations are accompanying features. Genetic factors have recently been shown to be involved.
NarcolepsyClassifications and external resources
| ICD-10 | G47.4 |
|---|---|
| ICD-9 | 347 |
Narcolepsy is a neurological condition most characterized by Excessive Daytime Sleepiness (EDS), episodes of sleep and disorder of REM or rapid eye movement sleep.
Symptoms
The main characteristic of narcolepsy is overwhelming excessive daytime sleepiness (EDS), even after adequate nighttime sleep.
Four other classic symptoms of narcolepsy, which may not occur in all patients, are:
Cataplexy: sudden episodes of loss of muscle function, ranging from slight weakness (such as limpness at the neck or knees, sagging facial muscles, or inability to speak clearly) to complete body collapse. Sleep paralysis: temporary inability to talk or move when waking up. Automatic behavior: Automatic behavior occurs when a person continues to function (talking, putting things away, etc.) during sleep episodes, but awakens with no memory of performing such activities. It is estimated that up to 40 percent of people with narcolepsy experience automatic behavior during sleep episodes.Daytime sleepiness, sleep paralysis, and hypnagogic hallucinations also occur in people who do not have narcolepsy, more frequently in people who are suffering from extreme lack of sleep.
In most cases, the first symptom of narcolepsy to appear is excessive and overwhelming daytime sleepiness. There are wide variations in the development, severity, and order of appearance of cataplexy, sleep paralysis, and hypnagogic hallucinations in individuals. The excessive daytime sleepiness generally persists throughout life, but sleep paralysis and hypnagogic hallucinations may not.
Although these are the common symptoms of narcolepsy, many (although less than 40% of people with narcolepsy)also suffer from insomnia for extended periods of time.
The symptoms of narcolepsy, especially the excessive daytime sleepiness and cataplexy, often become severe enough to cause serious problems in a person's social, personal, and professional lives and severely limit activities.
Effects
Normally, when an individual is awake, brain waves show a regular rhythm. 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. This sleep state, called rapid eye movement (REM) sleep, is when most remembered 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 muscular control, sleep paralysis, and vivid dreams -- occur at other times in people with narcolepsy. Sleep paralysis and vivid dreams can occur while falling asleep or waking up.
Simply put, the brain does not pass through the normal stages of dozing and deep sleep but goes directly into (and out of) rapid eye movement (REM) sleep. This has several consequences:
Nighttime sleep does not include much deep sleep, so the brain tries to "catch up" during the day, hence EDS People with narcolepsy fall quickly into what appears to be very deep sleep They wake up suddenly and can be disoriented when they do They have very vivid dreams, which they often rememberPeople with narcolepsy may dream even when they only fall asleep for a few seconds.
Causes
While the cause of narcolepsy has not yet been determined, scientists have discovered conditions that may increase an individual's risk of having the disorder. The protein produced, called hypocretin or orexin, is responsible for controlling appetite and sleep patterns.
The neural control of normal sleep states and the relationship to narcolepsy are only partially understood. In humans, narcoleptic sleep is characterized by a tendency to go abruptly from a waking state to REM sleep with little or no intervening non-REM sleep. The changes in the motor and proprioceptive systems during REM sleep have been studied in both human and animal models. During normal REM sleep, spinal and brainstem alpha motor neuron hypopolarization produces almost complete atonia of skeletal muscles via an inhibitory descending reticulospinal pathway. In narcolepsy, the reflex inhibition of the motor system seen in cataplexy is believed identical to that seen in normal REM sleep.
Narcolepsy is strongly associated with HLA DQB1*0602 genotype.
Despite the experimental evidence in human narcolepsy that there may be an inherited basis for at least some forms of narcolepsy, the mode of inheritance remains unknown.
Prevalence
It is estimated that there are as many as 3 million people worldwide affected by narcolepsy.
Narcolepsy can occur in both men and women at any age, although its symptoms are usually first noticed in teenagers or young adults.
Narcolepsy has its typical onset in adolescence and young adulthood.
The prevalence of narcolepsy in the United States has been estimated to be as high as one per 1,000. It is a reason for patient visits to sleep disorder centers, and with its onset in adolescence, it is also a major cause of learning difficulty and absenteeism from school. Normal teenagers often already experience excessive daytime sleepiness because of a maturational increase in physiological sleep tendency accentuated by multiple educational and social pressures;
Narcolepsy is much more common among men than among women.
Diagnosis
Diagnosis is relatively easy when all the symptoms of narcolepsy are present. But if the sleep attacks are isolated and cataplexy is mild or absent, diagnosis is more difficult.
Two tests that are commonly used in diagnosing narcolepsy are the polysomnogram and the multiple sleep latency test. These tests are usually performed by a sleep specialist. The polysomnogram involves continuous recording of sleep brain waves and a number of nerve and muscle functions during nighttime sleep. When tested, people with narcolepsy fall asleep rapidly, enter REM sleep early, and may awaken often during the night. The polysomnogram also helps to detect other possible sleep disorders that could cause daytime sleepiness.
For the multiple sleep latency test, a person is given a chance to sleep every 2 hours during normal wake times. Observations are made of the time taken to reach various stages of sleep. This test measures the degree of daytime sleepiness and also detects how soon REM sleep begins. Again, people with narcolepsy fall asleep rapidly and enter REM sleep early.
Treatment
Several treatments are available for narcolepsy. It is thought to be effective because it increases the quality of nocturnal sleep. For cataplexy and other REM-sleep symptoms, antidepressant medications and other drugs that suppress REM sleep are prescribed.
In addition to drug therapy, an important part of treatment is scheduling short naps (10 to 15 minutes) two to three times per day to help control excessive daytime sleepiness and help the person stay as alert as possible. Daytime naps are not a replacement for nighttime sleep.
Ongoing communication among the physician, the person with narcolepsy, and family members about the response to treatment is necessary to achieve and maintain the best control.
Research
Studies supported by the USA National Institutes of Health (NIH) are trying to increase understanding of what causes narcolepsy and improve physicians' ability to detect and treat the disease. Scientists are studying narcolepsy patients and families, looking for clues to the causes, course, and effective treatment of this sleep disorder.
Recent discovery of families of dogs that are naturally afflicted with narcolepsy has been of great help in these studies. Some of the specific questions being addressed in NIH-supported studies are the nature of genetic and environmental factors that might combine to cause narcolepsy and the immunological, biochemical, physiological, and neuromuscular disturbances associated with narcolepsy.
Scientists are also working to better understand sleep mechanisms and the physical and psychological effects of sleep deprivation and to develop better ways of measuring sleepiness and cataplexy.
Examples of areas of potential research include studies on the pathophysiology of narcolepsy;
Coping with narcolepsy
Learning as much about narcolepsy as possible and finding a support system can help patients and families deal with the practical and emotional effects of the disease, possible occupational limitations, and situations that might cause injury. A variety of educational and other materials are available from sleep medicine or narcolepsy organizations.
Support groups exist to help persons with narcolepsy and their families.
Individuals with narcolepsy, their families, friends, and potential employers should know that:
Narcolepsy is a life-long condition that requires continuous medication.Doctors generally agree that lifestyle changes can be very helpful to those suffering with narcolepsy. Suggested self-care tips, from the National Sleep Foundation, University at Buffalo, and Mayo Clinic, include:
Take several short daily naps (10-15 minutes) to combat excessive sleepiness and sleep attacks. Develop a routine sleep schedule – try to go to sleep and awaken at the same time every day.Investigations started in 2005 by the British Medical Association looked into the possibility of a cure for Narcolepsy.
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