Brain White Matter Network Study Of Patients In Parkinson's Disease With Cognitive Impairment Based Diffusion Tensor

Background and Objectives: Mild cognitive impairment(MCI)is common in Parkinson's disease with non-demmentia(PD-ND).Previous studies have shown that it is closely related to the damage of brain white matter,but the specific physiological mechanism is not clear.The study is based on technology of diffusion tensor imaging(DTI)and theory of complex network to explore the physiological mechanism of PD-MCI and provide objective evidence for its early diagnosis.Methods: Neuropsychological test,T1-weighted image(T1WI)and DTI from 71 patients with PD-ND and 31 healthy subjects.According to the relevant cognitive assessment scale,patients with PD-ND were divided into 43 patients with PD-NC and 28 patients with PD-MCI.T1 WI and DTI images were used to construct individual white matter networks(WMNs)in all subjects.By using SPSS software,global properties(clustering coefficient,local efficiency,characteristic path length and small-worldness),hubs and nodal efficiency were analyzed among three groups,and correlation between nodal efficiency and cognitive scores in patients with PD-ND was analyzed.Difference of connections in WMNs between PD-NC group and PD-MCI group by network based statistical analysis(NBS).Results:(1)Clustering coefficient and local efficiency have no significance,but characteristic path length and global efficiency have significant difference among three groups.And characteristic path length significantly increased and global efficiency is significantly reduced compared with HCs.In addition,WMNs of the three groups all have small-worldness,and compared with HCs,small-worldness of PD-MCI group significantly increased.(2)Hubs in WMNs of the three groups are nearly the same,and mainly located in limbic system(including cingulate gyrus,insula,caudate nucleus of bilateral hemisphere and left hippocampus),postcentral gyrus,middle occipital gyrus,precuneus,and putamen of bilateral hemisphere.Compared with HCs,PD-NC group and PD-MCI group also showed hubs in right angular gyrus,but not in left hippocampus.Compared with HCs and PD-NC group,PD-MCI group showed hubs in bilateral precentral gyrus.(3)Nodal efficiency of three groups have significant difference.Compared with HCs,nodal efficiency of PD-NC and PD-MCI group was reduced in hippocampus,parahippocampus gyrus,cingulate gyrus,temporal lobe,fusiform gyrus,amygdala,etc.Compared with PD-NC group,nodal efficiency of PD-MCI group is reduced in left medial orbital superior frontal gyrus.We also found nodal efficiency of many network nodes are significantly correlated with scores of global cognition,attention and working memory,memory and language,especially nodal efficiency in left medial orbital superior frontal gyrus was significantly related with several cognitive domains.(4)Compared with PD-NC group,there are many abnormal white matter fiber(WMF)connections among regions in PD-MCI group.Two abnormal subnetwoks are made up of many abnormal connetions and orbitofrontal cortex is the core,which involve the limbic system,basal ganglia and sensory area,etc.Conclusions: Research results confirmed relationships between PD-MCI and damage of WMFs among regions,mainly in the limbic system,especially the WMFs between orbitofrontal cortex and other brain regions,so network topological properties of orbitofrontal cortex may be a potential image marker of the early diagnosis of cognitive impairment in PD.