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)