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Background and Objectives: REM sleep behavior disorder (RBD) is a parasomnia characterized by dream enactment. The International RBD Study Group developed the RBD Symptom Severity Scale (RBDSSS) to assess symptom severity for clinical or research use. We assessed the psychometric and clinimetric properties of the RBDSSS in participants enrolled in the North American Prodromal Synucleinopathy (NAPS) Consortium for RBD., Methods: NAPS participants, who have polysomnogram-confirmed RBD, and their bedpartners completed the RBDSSS (participant and bedpartner versions). The RBDSSS contains 8 questions to assess the frequency and severity/impact of (1) dream content, (2) vocalizations, (3) movements, and (4) injuries associated with RBD. Total scores for participant (maximum score = 54) and bedpartner (maximum score = 38) questionnaires were derived by multiplying frequency and severity scores for each question. The Clinical Global Impression Scale of Severity (CGI-S) and RBD symptom frequency were assessed by a physician during a semistructured clinical interview with participants and, if available, bedpartners. Descriptive analyses, correlations between overall scores, and subitems were assessed, and item response analysis was performed to determine the scale's validity., Results: Among 261 study participants, the median (interquartile range) score for the RBDSSS-PT (participant) was 10 (4-18) and that for the RBDSSS-BP (bedpartner) was 8 (4-15). The median CGI-S was 3 (3-4), indicating moderate severity. RBDSSS-BP scores were significantly lower in women with RBD (6 vs 9, p = 0.02), while there were no sex differences in RBDSSS-PT scores (8 vs 10.5, p = 0.615). Positive correlations were found between RBDSSS-PT vs RBDSSS-BP (Spearman r s = 0.561), RBDSSS-PT vs CGI-S ( r s = 0.556), and RBDSSS-BP vs CGI-S ( r s = 0.491, all p < 0.0001). Item response analysis showed a high discriminatory value (range 1.40-2.12) for the RBDSSS-PT and RBDSSS-BP (1.29-3.47)., Discussion: We describe the RBDSSS with adequate psychometric and clinimetric properties to quantify RBD symptom severity and good concordance between participant and bedpartner questionnaires and between RBDSSS scores and clinician-assessed global severity.

Background and Objectives: Idiopathic/isolated REM sleep behavior disorder (iRBD) is associated with dementia with Lewy bodies and Parkinson disease. Despite evidence of abnormal cerebral perfusion in iRBD, there is currently no pattern that can predict whether an individual will develop dementia with Lewy bodies or Parkinson disease. The objective was to identify a perfusion signature associated with conversion to dementia with Lewy bodies in iRBD., Methods: Patients with iRBD underwent video-polysomnography, neurologic and neuropsychological assessments, and baseline 99m Tc-HMPAO SPECT to assess relative cerebral blood flow. Partial least squares correlation was used to identify latent variables that maximized covariance between 27 clinical features and relative gray matter perfusion. Patient-specific scores on the latent variables were used to test the association with conversion to dementia with Lewy bodies compared with that with Parkinson disease. The signature's expression was also assessed in 24 patients with iRBD who underwent a second perfusion scan, 22 healthy controls, and 19 individuals with Parkinson disease., Results: Of the 137 participants, 93 underwent SPECT processing, namely 52 patients with iRBD (67.9 years, 73% men), 19 patients with Parkinson disease (67.3 years, 37% men), and 22 controls (67.0 years, 73% men). Of the 47 patients with iRBD followed up longitudinally (4.5 years), 12 (26%) developed a manifest synucleinopathy (4 dementia with Lewy bodies and 8 Parkinson disease). Analysis revealed 2 latent variables between relative blood flow and clinical features: the first was associated with a broad set of features that included motor, cognitive, and perceptual variables, age, and sex; the second was mostly associated with cognitive features and RBD duration. When brought back into the patient's space, the expression of the first variable was associated with conversion to a manifest synucleinopathy, whereas the second was associated with conversion to dementia with Lewy bodies. The expression of the patterns changed over time and was associated with worse motor features., Discussion: This study identified a brain perfusion signature associated with cognitive impairment in iRBD and transition to dementia with Lewy bodies. This signature, which can be derived from individual scans, has the potential to be developed into a biomarker that predicts dementia with Lewy bodies in at-risk individuals.

Background and Objectives: Although orthostatic hypotension (OH) can be an early feature of autonomic dysfunction in isolated REM sleep behavior disorder (iRBD), no large-scale studies have examined the frequency of OH in iRBD. In this study, we prospectively evaluated the frequency of OH in a large multicenter iRBD cohort., Methods: Participants 18 years or older with video polysomnogram-confirmed iRBD were enrolled through the North American Prodromal Synucleinopathy consortium. All participants underwent 3-minute orthostatic stand testing to assess the frequency of OH, and a Δ heart rate/Δ systolic blood pressure (ΔHR/ΔSBP) ratio <0.5 was used to define reduced HR augmentation, suggestive of neurogenic OH. All participants completed a battery of assessments, including the Scales for Outcomes in Parkinson Disease-Autonomic Dysfunction (SCOPA-AUT) and others assessing cognitive, motor, psychiatric, and sensory domains., Results: Of 340 iRBD participants (65 ± 10 years, 82% male), 93 (27%) met criteria for OH (ΔHR/ΔSBP 0.37 ± 0.28; range 0.0-1.57), and of these, 72 (77%) met criteria for OH with reduced HR augmentation (ΔHR/ΔSBP 0.28 ± 0.21; range 0.0-0.5). Supine hypertension (sHTN) was present in 72% of those with OH. Compared with iRBD participants without OH, those with OH were older, reported older age of RBD symptom onset, and had worse olfaction. There was no difference in autonomic symptom scores as measured by SCOPA-AUT., Discussion: OH and sHTN are common in iRBD. However, as patients may have reduced autonomic symptom awareness, orthostatic stand testing should be considered in clinical evaluations. Longitudinal studies are needed to clarify the relationship between OH and phenoconversion risk in iRBD., Trial Registration Information: ClinicalTrials.gov: NCT03623672; North American Prodromal Synucleinopathy Consortium.