遗忘型轻度认知障碍脑灰质扩散张量成像特征研究

Characterization of the brain gray matter in amnestic mild cognitive impairmentby diffusion tensor imaging

目的既往研究多是利用扩散张量成像(DTI)研究脑白质特性以评估遗忘型轻度认知障碍(aMCI)和阿尔茨海默病(AD)患者。文中应用DTI中的平均扩散率(MD)评估aMCI和AD患者灰质微观结构完整性的损伤特征,从而判断其转化规律。方法回顾性分析南京大学医学院附属鼓楼医院2014年1月至2016年12月期间30例符合Petersen标准的aMCI患者(aMCI组)、30例AD患者(AD组)以及30例正常对照组(CN组)测量的全脑灰质MD值,构建灰质水分子平均扩散率网络,计算小世界网络特性,并与神经心理学评分进行相关性分析。结果与CN组相比,aMCI和AD组的灰质水分子平均扩散率网络显示出异常的小世界特性,即聚集程度较高和路径长度较长,反映了灰质微结构的损伤,且aMCI患者网络的平均连接度低于CN组,但高于AD组,差异均有统计学意义(P<0.05)。包括双侧海马和边缘系统的11个枢纽脑区灰质MD值和蒙特利尔认知评估量表得分呈负相关(P<0.05)。结论 aMCI脑灰质的水分子扩散特征有助于发现AD前期患者,并反映神经退行性疾病脑微观结构的破坏。

Objective Amnestic mild cognitive impairment （aMCI） and Alzheimer’s disease （AD）used to be evaluated by analyzing the characteristics of the brain gray matter via diffuse tensor imaging （DTI）. This study was to characterize the damage to the microstructural integrity of the brain gray matter in aMCI and AD patients using the mean diffusivity （MD） of DTI and to investigateits transformation rules.Methods This retrospective study included 30 cases ofaMCI, 30 cases of AD, and another 30 normal controls. We measured the MD values of the whole brain gray matter, established the MD network of the water molecules in the gray matter, characterized the small-world network, and performed correlation analysis by neuropsychological assessment.Results Compared with the normal controls, the MDnetworks of the aMCI and AD groupsexhibited abnormal small world characteristics, namely, a higher clustering coefficient and a longer path, which reflected the damage to themicrostructure of the gray matter, and theaverage connectivity in the aMCI patients was lowerthan that in thenormal controls but higher than that in the AD group（P〈0.05）. The MD values of the gray matter were negatively correlated with the Montreal Cognitive Assessment Scale scores in the 11 hub regions of the brain, including the bilateral hippocampus and the limbic system（P〈0.05）.Conclusion The diffusion feature of the water molecules in the brain gray matter of the aMCIpatient may help to detect early ADand reflect the damage to the brain microstructure in patients with neurodegenerative diseases.