Differential striatal dopamine binding in Parkinson's Disease with and without REM sleep behavior disorder: A Tc-99 m TRODAT-1 SPECT study

Background: Rapid eye movement (REM) sleep behavior disorder (RBD) is an early and significant prodromal marker for Parkinson's disease (PD). While the association between RBD and PD has been well-documented, the underlying pathophysiology differentiating PD patients with RBD (PD-RBD +) from those without RBD (PD-RBD-) remained unclear. This study aims to investigate the possible relationship between RBD and striatal dopamine depletion in de novo PD patients.

Methods: A retrospective, cross-sectional study was conducted on 151 PD patients. We used standard questionnaires and measurements to assess motor and nonmotor symptoms. The dopaminergic function was assessed utilizing Tc-99 m TRODAT-1 SPECT imaging, and statistical analyses were performed to compare dopamine transporter (DAT) binding between patients with or without probable RBD (pRBD).

Results: The PD-pRBD + group exhibited significantly lower DAT binding in the caudate nucleus (OR 0.618; 95% CI 0.392-0.618; p = 0.039) and putamen (OR 0.554; 95% CI 0.319-0.962; p = 0.036) compared to the PD-pRBD- group. The PD-pRBD + group also had a higher prevalence of non-motor symptoms, including depression (OR 7.499; 95% CI 2.770-20.299; p < 0.001) and constipation (OR 2.356; 95% CI 1.090-5.092; p = 0.029). Although trends toward increased dementia (12.3% in PD-pRBD + , 6.4% in PD-pRBD-, p = 0.266) and falls (16.4% in PD-pRBD + , 11.5% in PD-pRBD-, p = 0.482) were observed in the PD-pRBD + group, these did not reach statistical significance.

Conclusion: The presence of RBD in PD patients is associated with greater striatal dopaminergic dysfunction, suggesting a distinct subtype with potentially faster disease progression. These findings highlight the importance of early RBD identification in PD patients to guide more personalized interventions.