What is narcolepsy?

Narcolepsy is a chronic neurological disorder caused by the brain's inability to regulate sleep-wake cycles. Many people with narcolepsy also experience uneven and interrupted sleep that can involve waking up frequently during the night.

At various times throughout the day, people with narcolepsy experience overpowering bouts of sleep. If the urge becomes overwhelming, individuals will fall asleep for periods lasting from a few seconds to several minutes. In rare cases, some people may remain asleep for an hour or longer.

In addition to excessive daytime sleepiness (EDS), people with narcolepsy experience some or all of the typical symptoms of cataplexy (the sudden loss of voluntary muscle tone), vivid hallucinations during sleep onset or upon awakening, and brief episodes of total paralysis at the beginning or end of sleep called sleep paralysis.

Because narcolepsy is often misdiagnosed as other conditions, it may take years to get the proper diagnosis. The cause of narcolepsy remains unknown.

It is likely that narcolepsy involves multiple factors interacting to cause neurological dysfunction and sleep disturbances.

Is there any treatment?

There is no cure for narcolepsy. The U.S. Food and Drug Administration (FDA) approved the drug modafinil (a central nervous system stimulant) to treat EDS.

In cases where modafinil is not effective, doctors may prescribe amphetamine-like stimulants such as methylphenidate to alleviate excesive daytime sleepiness. Two classes of antidepressant drugs have proved effective in controlling cataplexy in many individuals: tricyclics (including imipramine, desipramine, clomipramine, and protriptyline) and selective serotonin reuptake inhibitors (including venlafaxine, fluoxetine, and sertraline).

The FDA also has approved sodium oxybate (also known as gamma hydroxybutyrate or GHB) to treat cataplexy and EDS in individuals with narcolepsy.

Drug therapy should accompany various behavioral strategies. For example, many people with narcolepsy take short, regularly scheduled naps at times when they tend to feel sleepiest.

Improving the quality of nighttime sleep can combat EDS and help relieve persistent feelings of fatigue.

Among the most important common-sense measures people with narcolepsy can take to enhance sleep quality are actions such as maintaining a regular sleep schedule, relaxing before bed, and avoiding large meals, alcohol, and caffeine-containing beverages before bedtime.

What is the prognosis?

None of the currently available medications enables people with narcolepsy to consistently maintain a fully normal state of alertness.

But EDS and cataplexy, the most disabling symptoms of the disorder, can be controlled in most patients with drug treatment. Often the treatment regimen is modified as symptoms change.

Whatever the age of onset, patients find that the symptoms tend to get worse over the two to three decades after the first symptoms appear. Many older patients find that some daytime symptoms decrease in severity after age 60.

What research is being done?

The National Institute of Neurological Disorders and Stroke (NINDS) supports investigations into the basic biology of sleep, including the brain mechanisms involved in generating and regulating sleep.

Within the National Heart, Lung, and Blood Institute, also a component of the NIH, the National Center on Sleep Disorders Research (NCSDR) coordinates Federal government sleep research activities and shares information with private and nonprofit groups.

NINDS-sponsored researchers are investigating the basic biology of sleep and conducting studies to further identify genetic and environmental factors that may cause narcolepsy.

Other researchers hope to better understand the genetic and biochemical bases of narcolepsy, which will eventually lead to new therapies to control symptoms and may lead to a cure.

Abnormalities in the immune system may plan an important role in the development of narcolepsy; NINDS researchers are working to understand why the immune system destroys hypocretin neurons in narcolepsy.