White matter microstructural alterations and brain metabolism distributions in Parkinson’s disease

This study aimed to use simultaneous ¹⁸F-FDG PET/MRI based on Automated Fiber Quantification (AFQ) to determine whether there is a relationship between white matter microstructure changes and glucose metabolism distribution in PD. The study involved 38 subjects, including 23 parkinson's disease (PD) patients and 15 age and sex-matched healthy controls (HC). Primary clinical data and cognitive assessments were collected. All subjects underwent a simultaneous ¹⁸F-FDG PET/MRI scan. AFQ was utilized to calculate tract-wise diffusion properties of 20 major white matter tracts. PD patients showed reduced mean Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores compared to HC subjects (P < 0.05). PD patients showed higher mean diffusivity (MD) (P = 0.047) and axial diffusivity (AD) (P = 0.02) along the right corticospinal tract (CST) compared to HC. The microstructural change of CST was mainly located in the parietal part (node 67-100). Compared to HC, PD patients had FDG hypermetabolism in the right paracentral lobule (P = 0.0204) and bilateral putamen (left: P = 0.0075; right: P = 0.0155) and hypometabolism in the right calcarine (P = 0.0489). Hypermetabolism was found in the right paracentral lobule, which connects with the cortex of the right CST, and positively correlated with MD (r = 0.612, P < 0.001) and AD (r = 0.516, P < 0.001). We observed microstructural changes and glucose metabolism distribution characteristics in PD patients. These results may provide imaging evidence for studying the pathology of PD.