Progressive brain changes in Parkinson's disease: A meta-analysis of structural magnetic resonance imaging studies

The progressive changes of brain structure in patients with Parkinson's disease (PD) remain controversial. To identify this controversy, a systematic review and meta-analysis of longitudinal magnetic resonance imaging studies in brain volume was performed. The percentage of volume change over time between patients with PD and healthy subjects of each brain region of interest was obtained. In total, 11 studies, comprising 833 cases (463 patients with PD and 370 healthy control subjects), were included for systematic review and meta-analysis. Ten brain regions were involved. Patients with PD in comparison with healthy controls showed significant progressive reductions in whole gray matter and caudate, putamen, accumbens, and amygdala volumes. Significant whole-brain atrophy from PD was also associated with cognitive dysfunction. The annual percentage of volume loss was -1.04% in whole-brain volume with cognitive decline, -1.16% in whole-brain volume in PD compared to PD with cognitive decline, -0.29% for whole gray matter, -0.62% for caudate, -0.97% for putamen, -3.55% for amygdala, and -5.40% for accumbens in patients with PD versus control subjects. Overall, our findings suggest that PD is related to progressive, regional brain atrophy, mainly affecting gray matter. However, due to existing confounding factors, the limited number of included studies, significant heterogeneity, and defective study design, the results should be interpreted with caution. Further confirmation is required by more studies with strict design, large samples, and unified paradigm.