Dream-enactment behaviors without REM sleep without atonia

Purpose: To compare clinical and polysomnographic features of patients with isolated REM sleep behavior disorder (iRBD) and patients with clinically reported dream-enactment behaviors (DEB) occurring in the absence of REM sleep without atonia (RSWA), and to clarify the clinical significance of DEB without RSWA. Methods: We retrospectively reviewed clinical records and polysomnography of consecutive patients referred to a tertiary sleep and neurology center. Twenty-six patients with polysomnography-confirmed iRBD, 21 patients with DEB without RSWA, and 24 control subjects were included. Clinical features related to prodromal neurodegeneration, neuroimaging findings, sleep architecture, REM atonia indices, limb movements, and respiratory parameters were analyzed using age-adjusted comparisons with effect size estimation. Results: Compared with DEB patients, iRBD patients were older and showed a higher prevalence of subtle extrapyramidal signs, lower cognitive performance, and a greater burden of vascular neuroimaging abnormalities. Clinically reported hyposmia and depression were infrequent and did not differ between groups. Both clinical groups exhibited increased sleep fragmentation and instability, most pronounced in iRBD, with DEB patients showing intermediate values. REM atonia robustly differentiated groups, whereas periodic limb movements during sleep and respiratory disturbance did not differ significantly after age adjustment. Conclusion: DEB occurring without RSWA are associated with a clinical and polysomnographic profile distinct from iRBD, characterized by preserved REM atonia and a lower burden of markers linked to prodromal neurodegeneration. These findings highlight the heterogeneity of DEB and support characterization beyond conventional RBD diagnostic criteria. Brief summary: Current knowledge/study rationale: Isolated REM sleep behavior disorder (iRBD) is defined by dream-enactment behaviors (DEB) with REM sleep without atonia (RSWA), whereas clinically reported DEB without RSWA presents a diagnostic challenge and unclear significance in relation to prodromal neurodegeneration. Study impact: In this retrospective tertiary-center cohort, iRBD patients had more extrapyramidal signs, lower cognitive performance, and greater vascular imaging abnormalities compared with DEB without RSWA, whereas both groups showed increased sleep instability. These findings highlight that DEB without RSWA has a distinct clinical and polysomnographic profile, supporting the need for characterization beyond conventional RBD diagnostic criteria.