Parasomnias can emerge in close association with OSA. The following associations have been noted between the two conditions (30).
1. OSA is becoming an increasingly recognized precipitant of sleepwalking (107,108). Guilleminault et al. (107) described 84 children (5 with sleep terrors and 79 with both sleep terrors and sleepwalking). Fifty-one (61%) of 84 children with parasomnia had a diagnosis of an additional sleep disorder: 49 with SDB and two with RLS. Forty-three of 49 children with SDB were treated with tonsillectomy, adenoidectomy, and/or turbinate revision. In all 43 children who received surgery, PSG performed three to four months later indicated the disappearance of SDB. The recordings also showed an absence of confusional arousals. In all surgically treated cases, parents also reported subsequent absence of the parasomnia. Parasomnias persisted in the six children who were untreated for SDB. Guilleminault et al. (109) studied CAP in 32 chronic sleepwalkers as well as age-matched normal controls and patients with mild SDB. More than 90% of these patients with mild SDB had UARS. Sleepwalkers on a nonsleepwalking night presented instability of NREM sleep, as demonstrated by CAP analysis of EEG activity. This instability was similar to the one noted in UARS patients. The authors suggest that subtle sleep disorders associated with chronic sleepwalking constitute the unstable NREM sleep background on which sleepwalking events occur. A subtle associated sleep disorder should be systematically searched for and treated in the presence of sleepwalking with abnormal CAP.
2. OSA-induced arousal from NREM sleep with complex or violent behaviors may be indistinguishable from primary disorders of arousal (confusional arousals, sleepwalking, and sleep terrors), nocturnal complex seizures, or nocturnal dissociative states. Time-synchronized video-PSG (VPSG) is essential for correct diagnosis. Espa et al. (117) studied 10 patients with sleepwalking, sleep terrors or both and 10 age- and sex-matched controls, who underwent PSG for three consecutive nights using esophageal pressure monitoring. Respiratory events occurred more frequently in parasomniacs than in controls. Respiratory effort seems to be responsible for the occurrence of a great number of arousal reactions in parasomniacs and is involved in triggering the parasomnia episodes.
3. Incidental association of RBD with OSA is sometimes noted and only VPSG can detect coexistence of both conditions. In a study by Olson et al. (110), PSGs of 93 subjects with RBD showed an AHI > 10 in 32 (34%) of the subjects.
4. OSA-induced arousals from REM sleep may mimic RBD ("pseudo-RBD"), with immediate post-arousal dream-related, complex or violent behaviors. Since OSA is a very common sleep disorder and OSA is most severe during REM sleep, this form of parasomnia may be more prevalent than currently believed. Iranzo and Santamaria (112) reported 16 patients presenting with dream-enacting behaviors and unpleasant dreams, in whom VPSG excluded RBD and was diagnostic of severe OSA, also demonstrating that the reported abnormal behaviors occurred only during apnea-induced arousals. Further, CPAP therapy eliminated the abnormal behaviors, unpleasant dreams as well as the snoring and daytime sleepiness. There have been other prior anecdotal reports of OSA simulating the clinical features of RBD but this is the first study with formal clinical and VPSG documentation (111,118). It is important to distinguish the two conditions because they have different pathophysiological substrates, and separate clinical and therapeutic implications.
5. Nasal CPAP therapy of OSA may result in SWS rebound with emergent confusional arousals, sleepwalking, sleep terrors, or a combination thereof. Millman et al. (119) report two episodes of sleepwalking in an adult on nasal CPAP during SWS rebound.
6. OSA-induced arousals from NREM (or occasionally REM) sleep may trigger repeated episodes of SRED (113,114).
7. SRED causing excessive weight gain may eventually induce clinical OSA (115).
8. OSA-induced cerebral anoxia and nocturnal seizures may present with complex or violent parasomnia-like behaviors. Parasomnias are a major cause of sleep-related violence, the current prevalence of which is reported to be about 2.1%, with males having a significantly higher rate than females; 38% is associated with dream-enacting behaviors (111). The other most frequently reported parasomnias in association with sleep-related violence are RBD and sleep terrors/sleepwalking, nocturnal dissociative disorders, nocturnal seizures, and OSA.
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