Pattern of cortical thickness in depression among early-stage Parkinson's disease: A potential neuroimaging indicator for early recognition

Purpose: This study aims to investigate the early change in cortical thickness and surface area in early-stage depressed PD (dPD) patients, and its associations with severity of depression. Methods: 59 patients with dPD, 27 patients with non-depressed PD (ndPD), and 43 healthy controls (HC) were recruited. The dPD patients were subclassified into mild-depressed PD (mi-dPD, n = 24), moderate-depressed PD (mo-dPD, n = 21) and severe-depressed PD (se-dPD, n = 14) subgroups. Structural MRI and surface-based morphometry analysis were applied to compare differences in cortical thickness and surface area among groups, and their correlations with Beck Depression Inventory (BDI) scores were analyzed. Results: Compared with ndPD, dPD exhibited cortical thinning in the dorsolateral prefrontal cortex (dlPFC, mainly involving the left superior frontal and bilateral middle frontal gyri), the right pars opercularis and bilateral lateral occipital gyri. The mean cortical thickness values within these regions negatively correlated with BDI scores. Subgroup analysis revealed that patients with mi-dPD had cortical thinning only in the right middle frontal gyrus, while se-dPD showed cortical thinning more extensively involving the right fusiform gyrus, posterior cingulate gyrus, and pars opercularis. There was no significant change in cortical surface area in either the dPD or its subgroups. Conclusion: Our findings indicated that PD-related depression was associated with decrease of cortical thickness, instead of surface area, of which the patterns correlated with the severity of depression. Cortical thinning in dlPFC, mainly involving the left middle frontal gyrus, may serve as a potential neuroimaging indicator for early recognition of depression in PD patients.