Sleep paralysis is also known as or subsumes Familial sleep paralysis and Isolated sleep paralysis. -ed.
In this clinical summary, Dr. Fabio Pizza and Dr. Federica Provini of IRCCS Istituto delle Scienze Neurologiche and the Department of Biomedical and Neuromotor Sciences at the University of Bologna in Bologna, Italy, detail the clinical and laboratory features of sleep paralysis, an intriguing REM sleep-related parasomnia found in a relevant number of otherwise normal subjects and associated but not coincidental with narcolepsy-cataplexy. Sleep paralysis may be familial and is thought to represent a disorder of REM sleep, whereby muscle atonia typical of REM sleep is concomitant with a wakeful conscious experience. The hallucinations of sleep paralysis seem to revolve around a core experience of “sensed presence” consistent with the hypothesis of REM sleep initiation of a threat-activated vigilance system.