MSH: A condition characterized by recurrent episodes of daytime somnolence and lapses in consciousness (microsomnias) that may be associated with automatic behaviors and AMNESIA. CATAPLEXY; SLEEP PARALYSIS, and hypnagogic HALLUCINATIONS frequently accompany narcolepsy. The pathophysiology of this disorder includes sleep-onset rapid eye movement (REM) sleep, which normally follows stage III or IV sleep. (From Neurology 1998 Feb;50(2 Suppl 1):S2-S7),CSP: recurrent, uncontrollable brief episodes of sleep and lapses in consciousness, often associated with hypnagogic hallucinations, cataplexy, automatic behaviors and sleep paralysis.,NCI: A sleep disorder characterized by a tendency for excessive sleepiness during the day which occurs even after adequate sleep in the nighttime. The persons who suffer from this condition experience fatigue and may fall asleep at inappropriate times during the day.