The exact cause of narcolepsy is not known.
An abnormality in the chemistry regulating sleep and wakefulness in the
brain is suspected, but not proven. Both genetic and environmental factors
are believed to play a role in the development of this disorder.
All patients experience excessive daytime sleepiness (sleep attacks and
persistent daytime drowsiness). Sleep attacks are short periods of sleep
that occur many times a day, regardless of the amount or quality of sleep
the night before. They are often described as irresistible and may occur
with or without warning when a person is driving, working, eating, talking,
or engaging in any other activity. Most patients also experience persistent
daytime drowsiness. Excessive
daytime sleepiness is usually the first symptom
of narcolepsy (link mirrored in case it isn't available - click
here) and often the most difficult symptom to control. The severity
of excessive daytime sleepiness varies; some patients may have many sleep
attacks each day and others o nly one or two sleep attacks per day.
Cataplexy refers to sudden, brief episodes of muscle weakness or
paralysis triggered by strong emotions such anger, laughter, surprise or
anticipation. Just as night-time REM (rapid eye movement) sleep is normally
accompanied by skeletal muscle paralysis and strong emotions (dreaming);
an intense emotion during the waking period can trigger instantaneous muscle
weakness or paralysis. Although unable to move, the person remains conscious.
For some people, any strong emotion may trigger cataplexy, while others
react to only certain specific emotions. Although most patients experience
cataplexy, some patients never develop this symptom. Hypnagogic
hallucinations are vivid, often frightening, dream-like images that
occur when dozing or when falling asleep. Sometimes these images are so
vivid that they are difficult to distinguish from reality. Sleep
paralysis refers to a temporary paralysis upon falling asleep or waking
up. Episodes may last only a few seconds to minutes. Frequent
awakenings at night are common, but are not the cause of excessive daytime
sleepiness in patients with narcolepsy.
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