基于DTI的早中晚期帕金森病脑白质网络拓扑属性改变研究

Diffusion tensor tractography reveals abnormal topological organization in white matter networks in mild,moderate and severe Parkinson’s disease

目的探讨早、中、晚期帕金森病(Parkinson disease,PD)患者脑白质网络拓扑属性的差异,寻找PD发生发展的脑网络变化特征表现。方法纳入66例PD患者和31例年龄、性别及教育年限相匹配的健康志愿者(对照组)。根据改良Hoehn-Yahr(H&Y)分级将PD患者分为早、中、晚期三组。所有受试者完成弥散张量成像(DTI)扫描,采用确定性纤维跟踪技术构建脑白质网络,进而基于复杂网络理论分析各组脑白质网络全局属性和局部属性的差异。结果(1)与对照组比较,PD组最短路径长度增加[中位数(四分位数间距):2.477(0.116)比2.428(0.115);Z=-2.553,P= 0.011],全局效率减低[中位数(四分位数间距):0.404(0.019)比0.412(0.019),Z=-2.553,P= 0.011]。PD组"小世界"属性保留(γ中位数4.585,四分位数间距0.511;λ=1.212±0.027;σ中位数3.786,四分位数间距0.335),但与之匹配的随机网络相比,真实网络的最短路径长度与聚类系数较对照组增加。PD组早、中、晚期组间全局属性比较均未见统计学差异(P> 0.05)。(2)局部属性分析显示:随病情严重程度加重,右侧尾状核、左侧楔前叶两个核心节点缺失,增加位于中央前回及中央后回的核心节点;PD组存在广泛脑区节点效率降低,主要集中在默认网络、突显网络、中央执行网络、视觉通路等重要脑区。PD晚期组较早期组左侧中央前回节点效率增加。结论 PD存在广泛脑区间的白质纤维受损,随病情严重程度加重,尾状核及皮层,尤其运动皮层网络结构改变可能是PD疾病进展特征性影像学标识。

Objective To investigate the difference of topological properties of the white matter networks(WMNs) in patients with Parkinson's disease(PD) in the mild,moderate and severe stages,and explore the changes of brain network characteristics during PD development.Methods Diffusion tensor imaging was performed in 66 PD patients and 31 age,sex and years of education matched healthy volunteers(control group).PD patients were stratified to mild,moderate and severe PD groups according to the modified Hochn and Yahr(HY) stage.The deterministic fiber tracking techniques were used to construct the white matter structural networks.Topological properties of the brain network were then calculated based on complex graph theory analysis to compare global and local parameters of the white matter structural networks in each group.Results(1) Compared with the control group,the shortest path length [2.477(0.116) vs.2.428(0.115),Z=-2.553,P=0.011]significantly increased and global efficiency [0.404(0.019) vs.0.412(0.019),Z =-2.553,P= 0.011] significantly reduced in the PD group,which indicated that the overall information transfer efficiency of the white matter networks decreased.In addition,the PD group retained the small-world attributes[γ=4.585(0.511),λ=1.212 ± 0.027,σ=3.786(0.335)].However,compared with the control group,the ratios of the shortest path length and clustering coefficient between the real networks and the random networks were significantly increased in the PD group.Nevertheless,there was no difference in global properties among the mild,moderate and severe PD groups(P0.05).(2)As the disease getting worse,PD patients lacked two hub regions in WM networks consisting of the right caudate nucleus and the left precuneus,but increased the postcentral gyrus and precentral gyrus as the hub regions.Moreover,significantly reduced nodal efficiency was found in a wide range of brain regions in the PD group,which mainly located in the key brain regions of the default mode network(DMN),central executive network(CEN) and salience network(SN),as well as the visual pathway.However,in the subgroup analysis,the difference was only found in the left precentral gyrus with the efficiency significantly increased in the severe PD group compared with that in the mild PD group.Conclusions Research results showed that there were extensive white matter fiber damage in PD and the changes in the network structure of the caudate nucleus and the cerebral cortex,especially the primary motor cortex might be a characteristic imaging manifestation of the progression in PD.