Pathophysiology of Parasomnias

Parasomnias may occur at the transition from wakefulness to non-rapid eye movement (NREM) sleep, e.g., hypnic starts, during NREM sleep, e.g., teeth grinding, head banging, sleep walking, confusional arousals, and sleep terrors, or during rapid eye movement or REM sleep, e.g., nightmares and REM sleep behavior disorder [1, 2]. The occurrence of parasomnias in preschool age children is almost ubiquitous. In a series of approximately 1000 children followed prospectively between the ages of 2 and 6 years, Petit et al. found that 88 % of children in their cohort had manifested at least one parasomnia during the study period [3]. The highest incidence of parasomnias is in preschool age children, with a gradual reduction into later childhood. Adults also experience parasomnias, though to a lesser degree than children. The observations of Mahowald and Schenck underscore the point that one of the key features of parasomnias is the dissociation of behaviors characteristic of one state (wakefulness/ REM sleep or NREM sleep) and their superimposition on to another state [1]. No satisfactory theory explains the clustering of NREM parasomnias into early childhood. A valid theory in this regard must explain the relative paucity of NREM parasomnias during the first 12 months of life, their frequent occurrence in preschool age children, and the gradual dissipation during the second decade.