Characterizing Parkinson's Disease Clinical and Biomarker Interactions in REM Sleep Behavior Disorder.

Area of Science:

• Neurology
• Biomarker Research
• Neurodegenerative Diseases

Background:

• REM Sleep Behavior Disorder (RBD) is a key early sign of synucleinopathies like Parkinson's Disease (PD).
• Understanding the relationship between RBD and PD progression is crucial for early diagnosis and intervention.

Purpose of the Study:

• To investigate the interplay of alpha-synuclein seed amplification assay (SAA), hyposmia, and dopamine transporter (DaT) SPECT imaging in individuals with RBD.
• To evaluate how phenoconversion and Movement Disorder Society (MDS)-Prodromal PD probability scores correlate with clinical symptoms and biomarker profiles in incident RBD patients.

Main Methods:

• Polysomnographically-confirmed RBD participants underwent clinical and biomarker assessments.
• Participants were categorized based on biomarker status (hyposmia, SAA, DaT) and clinical outcomes (MDS-Prodromal PD probability, phenoconversion).
• Performance on clinical assessments and biomarker presence were evaluated within these categories.

Main Results:

• Hyposmia correlated with reduced DaT binding and positive SAA.
• MDS-Prodromal PD Probability Scores predicted SAA positivity and phenoconversion.
• DaT positivity was significantly higher in phenoconverters (80%) compared to non-phenoconverters (10%).

Conclusions:

• Alpha-synuclein SAA positivity, DaT positivity, and hyposmia are strongly interconnected in RBD.
• MDS-Prodromal PD Probability scores show potential as predictors of near-term disease progression.
• These scores can serve as valuable stratification factors in clinical research for synucleinopathies.