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Narcolepsy is a brain disorder that disrupts your brain's normal sleep-wake cycle. You get strong urges to sleep at odd times of the day and suffer from severe daytime sleepiness — even if you are well-rested. You may find it hard to concentrate and may fall asleep without meaning to for several seconds or minutes.

Other narcolepsy symptoms include:

  • Sudden loss of muscle tone. This may involve some or all your body's muscles. You may even collapse. Strong emotions such as fear or laughter often trigger loss of muscle tone.
  • Being unable to move or speak while falling asleep or waking up.
  • Hallucinations (seeing things that aren't there) when falling asleep or waking up.

It can take many years after symptoms first start before a person finds out that he or she has narcolepsy. One reason is that many people do not know about the disorder and do not tell their doctors about their symptoms.

The cause of narcolepsy is not known, although genes seem to play a role. Narcolepsy cannot yet be cured. But there are medicines that can help control the sleepiness and loss of muscle tension.

If you have narcolepsy, getting the right medicines to control your symptoms is important in order to prevent accidents. Falling asleep or losing muscle control at the wrong time, such as when you're driving or walking down stairs, can lead to serious injury or death.

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Content last updated: September 22, 2009.

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