Sleep paralysis

Introduction
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By Fabio Pizza MD and Federica Provini MD

Sleep paralysis is also known as or subsumes Familial sleep paralysis and Isolated sleep paralysis. -ed.

In this clinical article, Dr. Fabio Pizza and Dr. Federica Provini of the Department of Neurological 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.

Key Points

  • Sleep paralysis is a REM sleep parasomnia characterized by an inability to perform voluntary movements associated with marked anxiety and occurs either at sleep onset (hypnagogic form) or on awakening (hypnopompic form).
  • Sleep paralysis attacks last some minutes, do not involve respiratory and ocular muscles, are fully reversible, and often are accompanied by terrifying dream images.
  • Sleep paralysis may form part of the narcoleptic tetrad, but isolated sleep paralysis occurs independently from narcolepsy, sometimes in a familial form.
  • Sleep paralysis is polysomnographically characterized by the presence of mixed REM-like and wake EEG or EMG features.