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Narcolepsy is a neurological disorder that causes episodes of unpreventable sleep. These episodes can occur frequently and at inappropriate times, for example while a person is talking, eating or driving. Although sleep episodes can occur at any time, they may be more frequent during periods of inactivity or monotonous, repetitive activity.
Narcolepsy occurs when the part of the brain that regulates sleep and wakefulness does not function properly, causing sudden spells of Rapid-Eye-Movement (REM) sleep – the dreaming state of sleep. These "sleep attacks” last from a few seconds to 30 minutes, regardless of the amount or quality of night time sleep. These attacks result in episodes of sleep at work and social events, while eating, talking, driving, or on other similarly inappropriate occasions.
Symptoms generally begin between the ages of 15 and 30. The four classic symptoms of the disorder (although not all sufferers will have all four) are:
- Excessive daytime sleepiness.
- Cataplexy: a striking, sudden episode of muscle weakness triggered by high emotions. Typically, the patient's knees buckle and may give way upon laughing, elation, fear, surprise or anger. In other typical cataplectic attacks the head may drop or the jaw may become slack. In severe cases, the patient might fall down and become completely paralysed for a few seconds to several minutes. Reflexes are abolished during the attack.
- Sleep paralysis: the patient suddenly finds himself unable to move for a few minutes, most often upon falling asleep or waking up.
- Hypnagogic hallucinations: dream-like auditory or visual hallucinations, while dozing or falling asleep.
Disturbed night time sleep, including tossing and turning in bed, leg jerks, nightmares, and frequent awakenings may also occur.
The development, number and severity of symptoms vary widely among individuals with the disorder but excessive sleepiness is usually the first and most prominent symptom of narcolepsy.
It is a frequent disorder, the second leading cause of excessive daytime sleepiness diagnosed by sleep centres after sleep apnea. Studies on the epidemiology of narcolepsy show an incidence of 0.2 to 1.6 per thousand in European countries, Japan and the United States.
In many cases diagnosis is not made until many years after the onset of symptoms. In one recent study, it took on average 14 years from the onset of symptoms to time of diagnosis. This is often due to the fact that patients consult a physician only after many years of excessive sleepiness, assuming that sleepiness is not indicative of a disease. Early diagnosis and treatment, however, are important to the physical and mental well-being of the sufferer, since studies have shown that even treated narcoleptic patients are often markedly psychosocially impaired in the area of work, leisure, interpersonal relations, and are more prone to accidents.
Narcolepsy can be diagnosed on the basis of a history of typical episodes and the results of an overnight sleep study with a multiple sleep latency test. The sleep study checks for other explanations that could account for daytime sleepiness, such as sleep deprivation, sleep apnoea and depression. The test is done in a sleep laboratory, where brain waves, eye movements, muscle activity, heartbeat, blood oxygen levels and respiration are monitored electronically with a device called a polysomnograph. The multiple sleep latency test is performed after an adequate night's sleep has been demonstrated clearly. Usually, it is done after a sleep study.
The 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 transition in REM sleep during at least two of the four naps. In contrast, normal subjects take an average of 12 to 14 minutes to fall asleep, and show no REM sleep.
There is at this time no cure for narcolepsy and there is no way to prevent narcolepsy but the symptoms can be controlled with behavioural and medical therapy. Excessive daytime sleepiness may be treated with stimulant drugs or with the drug modafinil. Cataplexy and other REM-sleep symptoms may be treated with antidepressant medications.
At best, medications will reduce the symptoms, but will not alleviate them entirely. Also, many currently available medications have side effects.
Lifestyle adjustments such as regulating sleep schedules, scheduled daytime naps and avoiding "over-stimulating" situations may also help to reduce the intrusion of symptoms into daytime activities.
People with narcolepsy have a significantly increased 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.
Although it is a life-long condition, most individuals with the narcolepsy enjoy a near-normal lifestyle with adequate medication and support from teachers, employers, and families. If not properly diagnosed and treated, narcolepsy may have a devastating impact on the life of the affected individual, causing social, educational, psychological, and financial difficulties
Further Information and Support
Narcolepsy & Overwhelming Daytime Sleep Society Of Australia (N.O.D.S.S.)
PO Box 100, Rosanna VIC 3084
Tel (03) 9761 9767 or (03) 9432 9669
Narcolepsy Association - UK
Narcolepsy Network Inc - USA
Center for Narcolepsy, Stanford School of Medicine - USA
National Institute of Neurological Disorders and Stroke - USA
Reviewed by: Dr Armin Mohamed, Department of Neurophysiology, Royal Prince Alfred Hospital, Sydney, Australia