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Classification and external resources
ICD-10 G47.4
ICD-9 347
OMIM 161400
DiseasesDB 8801
eMedicine neuro/522 
MeSH D009290


Narcolepsy is a chronic sleep disorder (a dyssomnia) characterized by overwhelming daytime drowsiness and sudden attacks of sleep. The condition is most characterized by excessive daytime sleepiness (EDS), in which a person experiences extreme tiredness and possibly falls asleep during the day at inappropriate times, such as at work or school. A narcoleptic will most probably experience disturbed nocturnal sleep, which is often confused with insomnia, and disorder of REM or rapid eye movement sleep.

Cataplexy, a sudden muscular weakness brought on by strong emotions, is a medical condition which may also affect narcoleptics. Often manifesting as muscular weaknesses ranging from a barely perceptible slackening of the facial muscles to the dropping of the jaw or head, weakness at the knees, or a total collapse. Usually only speech is slurred, vision is impaired (double vision, inability to focus), but hearing and awareness remain normal. In some rare cases, an individual's body becomes paralyzed and muscles will become stiff.

The term narcolepsy derives from the French word narcolepsie created in 1880 by the French physician Jean-Baptiste-Édouard Gélineau (1859-1928) by combining the Greek narke numbness, stupor and lepsis attack, seizure.[1]

[edit] Symptoms

The main characteristic of narcolepsy is excessive daytime sleepiness (EDS), even after adequate night time sleep. A person with narcolepsy is likely to become drowsy or fall asleep, often at inappropriate times and places. Daytime naps may occur without warning and may be physically irresistible. These naps can occur several times a day. They are typically refreshing, but only for a few hours. Drowsiness may persist for prolonged periods of time. In addition, night time sleep may be fragmented with frequent awakenings.

Four other "classic" symptoms of narcolepsy, which may not occur in all patients, are cataplexy, sleep paralysis, hypnagogic hallucinations, and automatic behavior. Cataplexy is an episodic condition featuring 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. Episodes may be triggered by sudden emotional reactions such as laughter, anger, surprise, or fear, and may last from a few seconds to several minutes. The person remains conscious throughout the episode. In some cases, cataplexy may resemble epileptic seizures.[2] Sleep paralysis is the temporary inability to talk or move when waking (or less often, falling asleep). It may last a few seconds to minutes. This is often frightening but is not dangerous. Hypnagogic hallucinations are vivid, often frightening, dreamlike experiences that occur while dozing, falling asleep and/or while awakening.

Automatic behavior means that 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. Sleep paralysis and hypnagogic hallucinations also occur in people who do not have narcolepsy, but more frequently in people who are suffering from extreme lack of sleep. Cataplexy is generally considered to be unique to narcolepsy and is analogous to sleep paralysis in that the usually protective paralysis mechanism occurring during sleep is inappropriately activated. The opposite of this situation (failure to activate this protective paralysis) occurs in rapid eye movement behavior disorder.

In most cases, the first symptom of narcolepsy to appear is excessive and overwhelming daytime sleepiness. The other symptoms may begin alone or in combination months or years after the onset of the daytime naps. There are wide variations in the development, severity, and order of appearance of cataplexy, sleep paralysis, and hypnagogic hallucinations in individuals. Only about 20 to 25 percent of people with narcolepsy experience all four symptoms. 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 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 life. 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. This sleep state, called REM sleep (rapid eye movement sleep), is when most remembered dreaming occurs. Associated with the EEG-observed waves during REM sleep, muscle atonia is present (called REM atonia).

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. For example, the lack of muscular control can occur during wakefulness in a cataplexy episode; it is said that there is intrusion of REM atonia during wakefulness. 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. Night time sleep does not include as much deep sleep, so the brain tries to "catch up" during the day, hence EDS. People with narcolepsy may visibly fall asleep at unpredicted moments (such motions as head bobbing are common). People with narcolepsy fall quickly into what appears to be very deep sleep, and they wake up suddenly and can be disoriented when they do (dizziness is a common occurrence). They have very vivid dreams, which they often remember in great detail. People with narcolepsy may dream even when they only fall asleep for a few seconds.

[edit] 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. Specifically, there appears to be a strong link between narcoleptic individuals and certain genetic conditions. One factor that may predispose an individual to narcolepsy involves an area of Chromosome 6 known as the HLA complex. There appears to be a correlation between narcoleptic individuals and certain variations in HLA genes, although it is not required for the condition to occur. Certain variations in the HLA complex are thought to increase the risk of an auto-immune response to protein-producing neurons in the brain. The protein produced, called hypocretin or orexin, is responsible for controlling appetite and sleep patterns. Individuals with narcolepsy often have reduced numbers of these protein-producing neurons in their brains.

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 depolarization produces almost complete atonia of skeletal muscles via an inhibitory descending reticulospinal pathway. Acetylcholine may be one of the neurotransmitters involved in this pathway. In narcolepsy, the reflex inhibition of the motor system seen in cataplexy is believed identical to that seen in normal REM sleep.[citation needed]

In 2004 researchers in Australia induced narcolepsy-like symptoms in mice by injecting them with antibodies from narcoleptic humans. The research has been published in the Lancet providing strong evidence suggesting that some cases of narcolepsy might be caused by autoimmune disease.[3] Narcolepsy is strongly associated with HLA DQB1*0602 genotype.[4] There is also an association with HLA DR2 and HLA DQ1. This may represent linkage disequilibrium.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. Some cases are associated with genetic diseases such as Niemann-Pick disease[5] or Prader-Willi syndrome.[6]

[edit] Epidemiology

It is estimated that as many as 3 million people worldwide are affected by narcolepsy. In the United States, it is estimated that this condition afflicts as many as 200,000 Americans, [7] but fewer than 50,000 are diagnosed. It is as widespread as Parkinson's disease or multiple sclerosis and more prevalent than cystic fibrosis, but it is less well known. Narcolepsy is often mistaken for depression, epilepsy, or the side effects of medications. It can also be mistaken for poor sleeping habits, recreational drug use, or laziness. Narcolepsy can occur in both men and women at any age, although its symptoms are usually first noticed in teenagers or young adults. There is strong evidence that narcolepsy may run in families; 8 to 12 percent of people with narcolepsy have a close relative with this neurologic disorder.

Narcolepsy has its typical onset in adolescence and young adulthood. There is an average 15-year delay between onset and correct diagnosis which may contribute substantially to the disabling features of the disorder. Cognitive, educational, occupational, and psychosocial problems associated with the excessive daytime sleepiness of narcolepsy have been documented. For these to occur in the crucial teen years when education, development of self-image, and development of occupational choice are taking place is especially damaging. While cognitive impairment does occur, it may only be a reflection of the excessive daytime somnolence.

The prevalence of narcolepsy is about 1 per 2,000 persons.[8] 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; this may be disabling with the addition of narcolepsy symptoms in susceptible teenagers. In clinical practice, the differentiation between narcolepsy and other conditions characterized by excessive somnolence may be difficult. Treatment options are currently limited. There is a paucity in the literature of controlled double-blind studies of possible effective drugs or other forms of therapy. Mechanisms of action of some of the few available therapeutic agents have been explored but detailed studies of mechanisms of action are needed before new classes of therapeutic agents can be developed. Narcolepsy is an underdiagnosed condition in the general population. This is partly because its severity varies from obvious to barely noticeable. Some people with narcolepsy do not suffer from loss of muscle control. Others may only feel sleepy in the evenings.

[edit] 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. It is also possible for cataplexy to occur in isolation. Two tests that are commonly used in diagnosing narcolepsy are the polysomnogram and the multiple sleep latency test (MSLT). 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 (sleep onset latency). 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.

[edit] Treatment

Treatment is tailored to the individual, based on symptoms and therapeutic response. The time required to achieve optimal control of symptoms is highly variable, and may take several months or longer. Medication adjustments are also frequently necessary, and complete control of symptoms is seldom possible. While oral medications are the mainstay of formal narcolepsy treatment, lifestyle changes are also important.

The main treatment of excessive daytime sleepiness in narcolepsy is with a group of drugs called central nervous system stimulants such as methylphenidate, racemic amphetamine, dextroamphetamine, and methamphetamine, or modafinil, a new stimulant with a different pharmacologic mechanism. In Fall 2007 an alert for severe adverse skin reactions to modafinil was issued by the FDA. [9] Other medications used are codeine[10] and selegiline. Another drug that is used is atomoxetine[11] (Strattera), a non-stimulant and Norepinephrine reuptake inhibitor (NRI), that has little or no abuse potential.[12] In many cases, planned regular short naps can reduce the need for pharmacological treatment of the EDS to a low or non-existent level.

Cataplexy and other REM-sleep symptoms are frequently treated with tricyclic antidepressants such as clomipramine, imipramine, or protriptyline, as well as other drugs that suppress REM sleep. Venlafaxine, a newer antidepressant which blocks the reuptake of serotonin and norepinephrine, has shown usefulness in managing symptoms of cataplexy[citation needed]. Gamma-hydroxybutyrate (GHB), a medication recently approved by the FDA, is the only medication specifically indicated for cataplexy. Gamma-hydroxybutyrate has also been shown to reduce symptoms of EDS associated with narcolepsy. While the exact mechanism of action is unknown, GHB is thought to improve the quality of nocturnal sleep.

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 between the health care provider, patient, and the patient's family members is important for optimal management of narcolepsy. Finally, a recent study reported that transplantation of hypocretin neurons into the pontine reticular formation in rats is feasible, indicating the development of alternative therapeutic strategies in addition to pharmacological interventions.[13]

Learning as much about narcolepsy as possible and developing a support system or finding a support group may help patients and families deal with the practical and emotional effects of the disorder, possible occupational limitations, and situations that might cause injury. Individuals with narcolepsy should avoid jobs that require driving long distances or handling hazardous equipment or that require alertness for lengthy periods. They may find it helps to take a nap before driving if possible or have a scheduled nap break during a long driving trip.

The National Sleep Foundation, University at Buffalo, and Mayo Clinic suggest it may help sufferers if they alert their employers, co-workers and friends in the hope that others will accommodate their condition and help when needed. The foundation say it may help if the sufferer breaks up larger tasks into small pieces and focuses on one small thing at a time, and if they carry a tape recorder, if possible, to record important conversations and meetings. The clinics say taking several short walks during the day may help sufferers.

[edit] Popular culture references

Depictions of the disorder in fiction and pop culture can range greatly in the accuracy of how they depict the symptoms. Narcolepsy is often depicted in an exaggerated fashion in comedy films or TV shows. In his book How to Talk Dirty and Influence People, comedian Lenny Bruce claimed to have struggled with the condition. In Thomas E Sniegoski's "The Sleeper Conspiracy" book series, a teen named Tom Lovett has narcolepsy. In the alien-invasion-themed video game Destroy All Humans!, the scientist Sleepy Ernst has narcolepsy.

[edit] Films and television

The French movie Narco portrays the disease.

The lead character in Gus Van Sant's film about young gay hustlers, My Own Private Idaho, played by River Phoenix, has narcolepsy. A dictionary definition of the condition is presented in the opening sequence. The acceptance and support he receives through these episodes by Keanu Reeves' character illustrates their humanity and counterpoints their dehumanizing work.

In the movie Rat Race, one of the main characters (Enrico Pollini, played by Rowan Atkinson) has narcolepsy as well as being very eccentric. This portrayal has been criticized for its accuracy and sensitivity of the disorder.

In the movie Moulin Rouge!, the Argentine has narcolepsy and falls through Christian's roof. This is how he is introduced to the Bohemians that will later take him to the Moulin Rouge.

In the movie Deuce Bigalow: Male Gigolo, a woman with narcolepsy was shown as the cause of several slap-stick accidents.

In the animated children's film Shrek the Third, Sleeping Beauty has narcolepsy, hence her name.

In the episode "Best Man for the GOB" of the quirky comedy Arrested Development, George Sr. hires a narcoleptic stripper in order to convince his accountant Ira Gilligan that he has killed the stripper in order to get him to leave town. A recurring guest character on the HBO crime drama The Sopranos was Aaron Arkaway, a devout fundamentalist Christian who has narcolepsy. He was dating Janice Soprano, who explained to her bemused family (when Aaron fell asleep at the dinner table) that "narcolepsy is an AMA-recognized dyssomnia."

In Ruby Gloom, Misery's cousin Malaise from the episode "Misery Loves Company" suffers from narcolepsy, causing her to fall asleep in the most untimely situations throughout the episode. In the novel Swindle, Character Ben admits to having Narcolepsy.

In the film Austin Powers: International Man of Mystery, Dr. Evil describes his father as having "low grade narcolepsy and a penchant for buggery".

In the animated series Galactic Football gatekeeper Ahito has narcolepsy - he often falls asleep in the field during matches.

In the American sitcom Frasier, Frasier Crane's brother Niles develops narcolepsy brought about by the stress of speaking to his ex-wife Maris's lawyers.

[edit] Music

In the song "Girls, Girls, Girls", Jay-Z mentions "Mami's a narcolyptic, always sleepin on Hov".

Singer and pianist Ben Folds wrote and performed a song called "Narcolepsy". The song was a metaphor for people's tendency to be emotionally numb during large life events. [14]

The band Placebo wrote a song called "Narcoleptic", on their album Black Market Music.

The band R.E.M., named for Rapid Eye Movement, has many lyrics about sleep, including "I don't sleep, I dream" and "Call me when you want to wake her up."

The band Third Eye Blind wrote a song called "Narcolepsy", describing the narcoleptic narrator's uncontrollable nightmares and sleep paralysis.

The Westchester punk band Plow United's third and final full length album was entitled Narcolepsy. The name of Australian band The Sleepy Jackson was inspired by a former drummer who has narcolepsy.

In the group, The Wiggles, the character Jeff possibly has narcolepsy as he sleeps far too much causing the others to constantly use the phrase, "Wake up, Jeff!"

The band 7 Car Pile-Up has a song called Narcoleptic Mime.

[edit] Anime and manga

In the anime and manga series One Piece, the main character Monkey D. Luffy, along with his brother Portgas D. Ace and his grandfather Monkey D. Garp are all narcoleptic, falling asleep during meals or fights. Luffy has even learned how to eat while sleeping because he does not like to miss the meals when he is sleeping.

In the anime and manga series Reborn!, the character Kyoya Hibari displays narcoleptic symptoms, his frequent and easily disturbed sleep being one of his many character quirks.

In the anime and manga series The Prince of Tennis, Jirou Akutagawa from the Hyotei Academy is narcoleptic. He spends most of his time sleeping during tennis matches, and he is nicknamed the "Sleeping Beauty of Hyotei".

In the anime series Kanon, main protagonist Yuichi Aizawa's cousin Nayuki has narcoleptic behaviors such as difficulty waking up even with her room filled with different alarm clocks and falling asleep at any time such as walking in the halls.

In the anime La Corda D'oro, Keiichi Shimizu, who plays the cello, demonstrates many symptoms of narcolepsy, including falling asleep as well as automatic behaviour.

In the anime Ghost Hound, the main protagonist character, Taro, has a slight case of narcolepsy.

In the visual novel Little Busters!, the main character Riki is narcoleptic.

The MV My Angel by Korean duo Fly to the Sky features a man with narcolepsy and his girlfriend. In this MV, narcolepsy plays a big part, causing the man to miss his job interview and fall off a high platform in a construction site. His girlfriend ends up dying due to him falling asleep on the motorcycle while bringing her to the hosipital after she falls off a ladder.

[edit] See also

[edit] References

  1. ^ Entry Narcolepsy. in the Online Etymology Dictionary. Douglas Harper, Historian. 18 Sep 2007.
  2. ^
  3. ^ "BBC News article". 
  4. ^ Maret, S; Tafti M (November 2005). "Genetics of narcolepsy and other major sleep disorders" (PDF). Swiss Medical Weekly (EMH Swiss Medical Publishers Ltd.) 135 (45-46): 662–665. PMID 16453205. Retrieved on 2008-03-07. 
  5. ^ "Sleep disturbances and hypocretin deficiency in Niemann-Pick disease type C". 
  6. ^ "Hypersomnia in the Prader Willi syndrome". 
  7. ^ "Who Is At Risk for Narcolepsy?". 
  8. ^ "Who Is At Risk for Narcolepsy?". 
  9. ^ Modafinil (marketed as Provigil): Serious Skin Reactions; FDA Drug Safety Newsletter
  10. ^ "Codeine treatment". 
  11. ^ "Stanford Center for Narcolepsy article". 
  12. ^ "Curtin University of Technology Article" (PDF). 
  13. ^ Arias-Carrión O, Murillo-Rodriguez E, Xu M et al (2004). "Transplantation of hypocretin neurons into the pontine reticular formation: preliminary results". Sleep 27 (8): 1465–1470. PMID : 15683135. 
  14. ^ Ben Folds Song Explanations

[edit] Sources

[edit] External links

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