36 Description of Parasomnias

The most recent consensus of the American Academy of Sleep Medicine is that parasomnias are “undesirable physical events or experiences that occur during entry into sleep, within sleep or during arousals from sleep” (1). Parasomnias are often considered to be normal sleep phenomena, especially in children, and do not in general have a serious impact on sleep quality or quantity. However, in some cases, injuries can result, psychological distress can ensue, and sleep disruption can seriously disturb the individual and family members. Sleep research has demonstrated, and still continues to accumulate evidence, that parasomnias are not homogeneous phenomena, but constitute a diverse group of conditions with different pathophysiologies and responses to treatment. They are currently classified into primary parasomnias (Table 1), which are disorders of sleep states per se, and secondary parasomnias, which are disorders of specific organ systems that manifest preferentially during sleep. Primary parasomnias are further classified into: (i) disorders of arousal (or NREM [nonREM] parasomnias), (ii) parasomnias associated with REM sleep, and (iii) other parasomnias. Disorders of arousal (from NREM sleep) are, in turn, comprised of confusional arousals, somnambulism (or sleepwalking), and sleep terrors. Parasomnias associated with REM sleep consist of nightmare disorder, recurrent isolated sleep paralysis (SP), and REM sleep behavior disorder (RBD). Classification of the other, residual parasomnias includes principally sleep enuresis, sleep-related bruxism, sleep-related rhythmic movement disorder, somniloquy (or sleep talking), and sleep-related groaning. In the following sections, the clinical features, polysomnographic characteristics, incidence, prevalence, and associated factors of each of these primary parasomnias is reviewed.