REM sleep without atonia (RSWA) is the polysomnographic finding of persistent muscle tone during REM sleep, resulting in paroxysmal phasic or tonic EMG activity. RSWA is essential for the diagnosis of REM sleep behavior disorder (RBD), but can also occur without dream-enacting behavior. Loss of atonia during REM sleep is considered as a biomarker for synucleinopathies. We will give an overview of the pathophysiology of RSWA and will highlight the diagnostic methods for RSWA. We will describe the different etiologies of RSWA and finally we will focus on the role of RSWA as biomarker for Lewy body disease. RSWA severity in isolated RBD patients is a potential predictor for early conversion to Parkinson's disease (PD) or dementia with Lewy bodies. In PD patients, RSWA severity is associated with more severe motor symptoms and disease progression. Future studies are needed to delineate the importance of isolated RSWA as prodromal marker of Lewy body disease.

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Mandibular advancement device (MAD) treatment outcome for obstructive sleep apnea (OSA) is variable and patient dependent. A global, clinically applicable predictive model is lacking. Our aim was to combine characteristics obtained during drug-induced sleep endoscopy (DISE), awake nasendoscopy, and computed tomography scan-based computational fluid dynamic (CFD) measurements in one multifactorial model, to explain MAD treatment outcome. A total of 100 patients with OSA were prospectively recruited and treated with a MAD at fixed 75% protrusion. In all, 72 underwent CFD analysis, DISE, and awake nasendoscopy at baseline in a blinded fashion and completed a 3-month follow-up polysomnography with a MAD. Treatment response was defined as a reduction in the apnea-hypopnea index (AHI) of ≥50% and deterioration as an increase of ≥10% during MAD treatment. To cope with missing data, multiple imputation with predictive mean matching was used. Multivariate logistic regression, adjusting for body mass index and baseline AHI, was used to combine all potential predictor variables. The strongest impact concerning odds ratios (ORs) was present for complete concentric palatal collapse (CCCp) during DISE on deterioration (OR 28.88, 95% confidence interval [CI] 1.18-704.35; p = 0.0391), followed by a C-shape versus an oval shape of the soft palate during wakefulness (OR 8.54, 95% CI 1.09-67.23; p = 0.0416) and tongue base collapse during DISE on response (OR 3.29, 95% CI 1.02-10.64; p = 0.0464). Both logistic regression models exhibited excellent and fair predictive accuracy. Our findings suggest DISE to be the most robust examination associated with MAD treatment outcome, with tongue base collapse as a predictor for successful MAD treatment and CCCp as an adverse DISE phenotype.

ObjectiveTo quantitatively investigate the effect of mandibular advancement devices (MADs) on pharyngeal airway dimensions in a transverse plane as measured during drug‐induced sleep endoscopy (DISE).MethodsData from 56 patients, treated with MAD at 75% maximal protrusion and with baseline Apnea‐Hypopnea Index ≥10 events/h, were analyzed. For each patient, three snapshots were selected from DISE video footage at baseline, with MAD presence, and during chin lift, resulting in 498 images (168/168/162, baseline/MAD/chin lift). Cross‐sectional areas, anteroposterior (AP) and laterolateral (LL) dimensions on both retroglossal and retro‐epiglottic levels were measured. To define the effect of MAD and chin lift on pharyngeal dimensions, linear mixed‐effect models were built. Associations between MAD treatment response and pharyngeal expansion (MAD/chin lift) were determined.ResultsSignificant differences were found between retroglossal cross‐sectional areas, AP, and LL dimensions at baseline and with MAD presence. At a retro‐epiglottic level, only LL dimensions differed significantly with MAD presence compared to baseline, with significant relation of LL expansion ratio to treatment response (p = 0.0176). After adjusting the response definition for the sleeping position, greater retroglossal expansion ratios were seen in responders (1.32 ± 0.48) compared to non‐responders (1.11 ± 0.32) (p = 0.0441). No significant association was found between response and pharyngeal expansion by chin lift.ConclusionOur observations highlight the additional value of quantitative pharyngeal airway measurements during DISE with MAD presence in evaluating MAD treatment outcome. These findings demonstrate an increase in retroglossal airway dimensions during DISE, with MAD presence, and more pronounced increase in retroglossal expansion ratios in MAD treatment responders compared to non‐responders after sleeping position correction.Level of Evidence3 Laryngoscope, 2023