Narcolepsy is a sleep disorder defined by constant sleepiness and a tendency to sleep at inappropriate times. Typically, a person with narcolepsy suffers sleep attacks as well as continual sleepiness and a feeling of tiredness that is not completely relieved by any amount of sleep.
The four most common symptoms of narcolepsy are:
Cataplexy (sudden loss of strength in the muscles)
Excessive daytime sleepiness
Hypnagogic hallucinations (hallucinations that occur just before falling asleep, during a naps, and/or on waking up)