Narcolepsy is a disorder characterized by sudden, brief, uncontrollable episodes of REM sleep at inappropriate times. Cataplexy is an abrupt loss of muscle tone, usually triggered by strong emotions. This transient weakness or paralysis occurs while the patient is conscious, and can manifest as anything from slurred speech to complete collapse. Cataplexy is frequently associated with narcolepsy. Other symptoms of narcolepsy include excessive daytime sleepiness, hypnagogic hallucinations, and sleep paralysis.