Background: The role of nigrostriatal dopaminergic neurons degeneration is well established in the pathophysiology of Parkinson’s disease. However, it is unclear if and how the degeneration of the dopamine pathways affects the manifestation of the neuropsychiatric symptoms (NPS) of Parkinson’s disease (PD). Dopamine transporter (DAT) imaging, a technique to measure the reduction in dopamine transporters is increasingly used as a tool in the diagnosis of PD.
Methods: In this study, we examine if the baseline dopamine transporter density in the striatum
measured by the striatal binding ratio (SBR) is associated with the longitudinal onset and/or pro-
gression of NPS in PD as measured by part 1 of Movement Disorder Society - Unified Parkinson's
Disease Rating Scale, over four years. Data of patients with PD and an abnormal screening present
on 123I-ioflupane single-proton emission computed tomography were obtained from Parkinson's
Progression Markers Initiative (PPMI) database. Latent Growth Modeling (LGM), a statistical tech-
nique that can model the change over time while considering the variability in the rate of change at
the individual level, was used to examine the progression of NPS over time.
Results: The results indicate the SBR did not correlate with the baseline NPS but did correlate with
the rate of change of NPS (p<0.001) over the next four years, even after eliminating age-related
variance, which can be a significant confounding factor.
Conclusion: In conclusion, this study showed gradual worsening in NPS in patients with Parkinson’s disease, which inversely correlates with the density of the dopamine transporters as measured
by SBR at baseline.