对主观认知下降人群基于TBSS白质损伤的研究

Tract-based spatial statistics analysis of white matter changes in subjects with subjective cognitive decline

目的:本研究通过基于纤维束示踪的空间统计方法(Tract-based spatial statistics,TBSS)分析主观认知下降(Subjective cognitive decline,SCD)人群的核磁弥散张量成像(Magnetic resonance diffusion tensor imaging,MR-DTI)的影像数据,观察SCD阶段是否存在脑结构异常。方法:收集27个临床诊断为SCD的患者为SCD组,另选取37个正常老年人为对照组(Normal controls,NC),他们的年龄、性别和教育互相匹配。采用TBSS分析方法对MR-DTI影像数据预处理后SCD组和NC组的各向异性分数(Fractional anisotropy,FA)、平均弥散系数(Mean diffusivity,MD)、径向弥散系数(Radial diffusivity,RD)、轴向弥散系数(Axial diffusivity,AxD)进行基于体素的全脑非参数统计学比较,并且分析与认知功能的相关性。结果:与正常对照组比较,SCD组FA值显著减小及MD、RD增高的纤维束主要位于胼胝体(膝部、体部、压部),双侧放射冠、上下纵束、内囊、额枕上下束、外囊、穹窿,右侧扣带回、丘脑后辐射和左侧钩束,AxD未发现异常。相关性分析发现MD与听觉词语学习测验(Auditory verbal learning test,AVLT)即刻及延迟记忆分数存在显著负相关(P<0.05),RD与AVLT延迟记忆分数存在负相关(P<0.05),未发现FA、MD和RD与MMSE和MoCA评分存在相关。结论:在SCD阶段,患者白质纤维损害已经存在,并且分布广泛,MD和RD与记忆功能相关联,提示在SCD阶段已经出现病理改变,并早于临床认知功能减退。

Objective： To analyze the magnetic resonance diffusion tensor imaging （MR-DTI） datas in patients with subjec- tive cognitive decline （SCD） using tract based spatial statistics （TBSS）, to observe brain structural changes in the SCD phase. Methods： Twenty-seven SCD subjects and 37 age-, sex- and education-matched normal controls （NC） were employed in this study. Whole-brain diffusion tensor imaging （DTI） and a battery of neuropsychological tests, including mini-mental state exami- nation（MMSE）, montreal cognitive assessment（MoCA） and auditory verbal learning test（AVLT）, were acquired on every subject. To figure out the white matter impairments regions of SCD, we conducted two sample t-test between SCD and NC by tract- based spatial statistics（TBSS） analysis on fractional anisotropy（FA） maps. Mean and max values of FA in the regions of white matter impairments were also obtained to investigate the relationship with the neuropsychological tests scores. Mean diffusivity （MD）, radial diffusivity （RD） and axial diffusivity were analyzed in the similar manner. Results： Compared with NC, the SCD group showed decreased FA and increased MD and RD and unchanged AxD in corpus callosum, bilateral corona radiata, infe- rior longitudinal fascieulus, superior longitudinal fasciculus, internal capsule, superior fronto-occipital fasciculus, inferior fronto- occipital faseiculus, external capsule, fornix, and right cingulate gyrus, thalamic radiation, and left uncinate fasciculus. MD values were significantly negatively correlated with AVLT learning and delayed recall（P〈0.05）. RD values were negatively cor- related with AVLT delayed recall （P〈0.05）. FA, MD and RD were not markedly correlated with MMSE and MoCA. Conclu- sions： Extensive white matter（WM） damage were observed in SCD. In addition, the MD, RD values were associated with mem- ory function. It might indicated that the SCD subjects had suffered from the pathological changes, while the oathological changes were unable detected by conventional objective neuropsychological tests.