Parasomnias

Parasomnias are defined as unpleasant or undesirable behavioral or experiential phenomena which occur predominately or exclusively during the sleep period. Initially thought to represent a unitary phenomenon, typically attributed to psychiatric disease, it is now clear that parasomnias are the manifestation of a wide variety of completely different conditions, most of which are diagnosable and treatable. The parasomnias may be conveniently categorized as 'primary sleep parasomnias' (disorders of the sleep states per se) and 'secondary sleep parasomnias' (disorders of other systems which manifest themselves during sleep). The primary sleep parasomnias can be classified according to the sleep state of origin: rapid eye movement (REM) sleep, nonrapid eye movement (NREM) sleep, or miscellaneous (i.e., those not respecting sleep state). The secondary sleep parasomnias can be further classified by the organ system involved. Most parasomnias can be explained by the fact that sleep is not necessarily a global or 'whole brain' phenomenon. Rather, the states of wakefulness, NREM sleep, and REM sleep may become admixed or oscillate rapidly, resulting in complex behaviors occurring without conscious awareness.