Brain Structural Alteration In Parkinson's Disease With Depression

Background and Objectives: Depression is common in patients with Parkinson's disease,which reduces the quality of life of patients and impairs their ability to function in their daily lives,but its pathophysiological mechanisms are unclear.The present study aimed to investigate alterations in brain cortical thickness related to depression in Parkinson's disease and their correlations with structural impairments of white matter.Methods: Twenty-nine Parkinson's disease patients with depression(dPD),21 Parkinson's disease patients without depression(ndPD),and 26 healthy controls(HC)were enrolled in the study.All subjects were assessed with the Hamilton Depression Scale,the Hamilton Anxiety Scale,and the Mini-Mental State Examination.All subjects underwent 3D-T1 WI and diffusion tensor imaging(DTI)on a 3.0T magnetic resonance scanner.Cortical thickness differences were assessed using FreeSufer software and analyzed for association with severity of depression.Based on the brain region with abnormal cortical thickness,the integrity of the white matter fiber tract associated with the abnormal brain region was evaluated by calculating the FA value and MD value and analyzed for association with the cortical thickness and the severity of depression.Results: Cortical thickness were decreased in the right fusiform gyrus and right posterior cingulate cortex in dPD compared to ndPD with no direct correlation with Hamilton Depression Scale score.In addition,Cortical thickness were decreased in the bilateral lateralorbitofrontal,bilateral medial-orbitofrontal,bilateral fusiform gyrus,left cuneus,right precuneus cortex in dPD compared to HC.In the DTI analysis,Increased MD value was found in the left cingulum tract in dPD compared to ndPD.In addition,Increased MD value was found in the left uncinate fasciculus in dPD compared to HC and was negatively correlated with the cortical thickness of the left posterior cingulate gyrus,the left fusiform gyrus,the left lateral-orbitofrontal,the left medial-orbitofrontal.Conclusions: we found that the posterior cingulate gyrus of abnormal cortical thickness is a region belonging to the default mode network(DMN),involved in self-referential processing and mood control.Our results indicate that the damage of the cingulate gyrus structure may indirectly damage DMN,resulting the occurrence of depression in Parkinson's disease.In the DTI analysis,it was found that the integrity of the fiber tract associated with the cerebral regions with abnormal cortical thickness was impaired and mainly distributed in the prefrontal-limbic system regions,suggesting that the abnormal structure of the prefrontallimbic system regions might be related to the occurrence of depression in Parkinson's disease.Therefore,the results of this study suggest that depression in Parkinson's disease may be associated with impaired DMN and prefrontal-limbic system regions,and also provides the imaging support of brain morphology and structure connection for the abnormal brain function connection of dPD.