Clinical subtypes in patients with isolated REM sleep behaviour disorder.

Patients with Parkinson's disease (PD) show a broad heterogeneity in clinical presentation, and subtypes may already arise in prodromal disease stages. Isolated REM sleep behaviour disorder (iRBD) is the most specific marker of prodromal PD, but data on clinical subtyping of patients with iRBD remain scarce. Therefore, this study aimed to identify iRBD subtypes. We conducted comprehensive clinical assessments in 66 patients with polysomnography-proven iRBD, including motor and non-motor evaluations, and applied a two-step cluster analysis. Besides, we compared iRBD clusters to matched healthy controls and related the resulting cluster solution to cortical and subcortical grey matter volumes by voxel-based morphometry analysis. We identified two distinct subtypes of patients based on olfactory function, dominant electroencephalography frequency, amount of REM sleep without atonia, depressive symptoms, disease duration, and motor functions. One iRBD cluster (Cluster I, late onset-aggressive) was characterised by higher non-motor symptom burden despite shorter disease duration than the more benign subtype (Cluster II, early onset-benign). Motor functions were comparable between the clusters. Patients from Cluster I were significantly older at iRBD onset and exhibited a widespread reduction of cortical grey matter volume compared to patients from Cluster II. In conclusion, our findings suggest the existence of clinical subtypes already in the prodromal stage of PD. Future longitudinal studies are warranted that replicate these findings and investigate the risk of the more aggressive phenotype for earlier phenoconversion and dementia development.

Evaluation of a Structured Screening Assessment to Detect Isolated Rapid Eye Movement Sleep Behavior Disorder.

BACKGROUND: Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) cohorts have provided insights into the earliest neurodegenerative processes in α-synucleinopathies. Even though polysomnography (PSG) remains the gold standard for diagnosis, an accurate questionnaire-based algorithm to identify eligible subjects could facilitate efficient recruitment in research. OBJECTIVE: This study aimed to optimize the identification of subjects with iRBD from the general population. METHODS: Between June 2020 and July 2021, we placed newspaper advertisements, including the single-question screen for RBD (RBD1Q). Participants' evaluations included a structured telephone screening consisting of the RBD screening questionnaire (RBDSQ) and additional sleep-related questionnaires. We examined anamnestic information predicting PSG-proven iRBD using logistic regressions and receiver operating characteristic curves. RESULTS: Five hundred forty-three participants answered the advertisements, and 185 subjects fulfilling inclusion and exclusion criteria were screened. Of these, 124 received PSG after expert selection, and 78 (62.9%) were diagnosed with iRBD. Selected items of the RBDSQ, the Pittsburgh Sleep Quality Index, the STOP-Bang questionnaire, and age predicted iRBD with high accuracy in a multiple logistic regression model (area under the curve >80%). When comparing the algorithm to the sleep expert decision, 77 instead of 124 polysomnographies (62.1%) would have been carried out, and 63 (80.8%) iRBD patients would have been identified; 32 of 46 (69.6%) unnecessary PSG examinations could have been avoided. CONCLUSIONS: Our proposed algorithm displayed high diagnostic accuracy for PSG-proven iRBD cost-effectively and may be a convenient tool for research and clinical settings. External validation sets are warranted to prove reliability. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.