Narcolepsy with cataplexy is a state of sleepiness in the waking hours characterized by diminished muscle control and the urge to fall asleep. This condition is very similar to REM sleep because the brain functions are active as in wakefulness during REM sleep. Moreover, the loss of voluntary muscle control and diminished muscle tone is typical for both conditions. Another important similarity between REM sleep and narcolepsy with cataplexy is the presence of hallucinations in the form of dreams. However, in REM sleep, these dreams are experienced during sleep, while in narcolepsy with cataplexy, they are encountered during wakefulness.
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