Hypoperfusion in Alzheimer’s Disease–Prone Regions and Dementia Conversion in Parkinson’s Disease

Purpose of the Report Although early detection of individuals at risk of dementia conversion is important in patients with Parkinson’s disease (PD), there is still no consensus on neuroimaging biomarkers for predicting future cognitive decline. We aimed to investigate whether cerebral perfusion patterns on early-phase 18F-N-(3-fluoropropyl)-2β-carboxymethoxy-3β-(4-iodophenyl) nortropane (18F-FP-CIT) PET have the potential to serve as a neuroimaging predictor for early dementia conversion in patients with PD. Materials and Methods In this retrospective analysis, we enrolled 187 patients with newly diagnosed PD who underwent dual-phase 18F-FP-CIT PET at initial assessment and serial cognitive assessments during the follow-up period (>5 years). Patients with PD were classified into 2 groups: the PD with dementia (PDD)-high-risk (PDD-H; n = 47) and the PDD-low-risk (PDD-L; n = 140) groups according to dementia conversion within 5 years of PD diagnosis. We explored between-group differences in the regional uptake in the early-phase 18F-FP-CIT PET images. We additionally performed a linear discriminant analysis to develop a prediction model for early PDD conversion. Results The PDD-H group exhibited hypoperfusion in Alzheimer’s disease (AD)-prone regions (inferomedial temporal and posterior cingulate cortices, and insula) compared with the PDD-L group. A prediction model using regional uptake in the right entorhinal cortex, left amygdala, and left isthmus cingulate cortex could optimally distinguish the PDD-H group from the PDD-L group. Conclusions Regional hypoperfusion in the AD-prone regions on early-phase 18F-FP-CIT PET can be a useful biomarker for predicting early dementia conversion in patients with PD.