复发缓解型多发性硬化患者默认网络的功能与结构连接的MRI研究

Functional and structural connectivity abnormalities of default mode network in relapsing-remitting multiple sclerosis： a study combining functional MRI and diffusion tensor imaging

目的 应用静息态fMRI、DTI技术对复发缓解型多发性硬化（RRMS）患者默认网络（DMN）功能与结构连接进行研究,探讨其特征性改变及两者间的相互关系.方法 收集2011年3月至2012年3月临床诊断为RRMS的患者27例,年龄和性别相匹配的健康志愿者27名作为正常对照组.分别行3.0TMR脑静息态fMRI及DTI扫描,运用DPARSF、MICA、TrackVis等多种软件对数据进行后处理,以DMN中的前额皮质中部（mPFC）和后扣带回（PCC）为ROI,分析RRMS患者与正常对照组默认网络功能与结构连接的改变,并获得2组的DMN反映功能连接强度的时间相关系数（r值）和结构连接的平均各向异性分数（FA）值,运用两样本t检验及Pearson相关性分析等统计学方法对结果进行统计分析.结果 RRMS组的DMN与对照组的空间网络分布基本一致,但功能连接有所改变,表现为mPFC的功能连接增强,而PCC、顶下小叶（IPL）的功能连接减弱;RRMS组PCC-mPFC间的平均r值（0.695±0.151）明显低于正常对照组平均r值（0.796±0.085）,差异具有统计学意义（t=-3.020,P＜0.05）;RRMS组PCC-mPFC间的FA值（0.261±0.012）明显低于正常对照组FA值（0.285±0.017）,差异也具有统计学意义（t=-6.206,P＜0.05）.r值和FA值呈显著正相关（RRMS组和对照组相关系数分别为0.704和0.735,P值均＜0.01）;病灶个数与r值、FA值均无相关性.结论 RRMS患者存在DMN的异常,表明RRMS患者DMN存在功能的重构或代偿.患者组DMN网络内mPFC-PCC间的功能连接和结构连接较对照组均减弱且存在相关性,表明功能连接强度减弱存在对应的结构基础.

Objective To investigate the functional and structural changes of connectivity of default mode network （DMN） in relapsing-remitting multiple sclerosis （RRMS） by functional MRI （fMRI） and diffusion tensor imaging （DTI） and to study the relationship between them.Methods Twenty-seven RRMS patients（clinically diagnosed as RRMS）and 27 healthy volunteers （matched to the patients in age and gender） were selected to participate in this study.All the subjects underwent 3.0 T MR scanning.Softwares such as DPARSF,MICA,TrackVis were used for data post-processing.Medial prefrontal cortex （mPFC） and posterior cingulate cortex（PCC） of DMN were chosen as ROIs,and functional and structural changes of DMN and the relationship between them were analyzed.Values of r reflecting the functional connectivity and fractional anisotropy（FA） of two groups were obtained.Then statistical analysis was performed by using student t test and Pearson correlation analysis.Results The DMN space pattern of the RRMS patients was mostly identical to that of controls,but with specific difference in the connectivity strength with respect to that of controls.Particularly,the patient group showed increased DMN connectivity in the mPFC,but decreased connectivity in the inferior parietal lobule （IPL） and PCC.Compared with controls,the r value （0.695 ±0.151 vs.0.796±0.085）,FA value（0.261 ±0.012 vs.0.285 ±0.017） between mPFC and PCC in RRMS patients were decreased （t =-3.020,-6.206,P 〈 0.05）.In addition,functional connectivity （r value） was found to correlate with structural connectivity（FA value） between the PCC and mPFC （r =0.704,0.735,P 〈 0.01）.The number of MS lesion,had no correlation with r value or FA value （P 〉 0.05）.Conclusions The functional connectivity and structural connectivity of DMN change in RRMS patients.The functional connectivity and structural connectivity between mPFC and PCC are both decreased in RRMS patients compared with the controls.The injury of structural connectivity may be the structural basis of the decrease of functional connectivity.