早期阿尔茨海默病脑白质改变和认知功能损伤的相关性

目的 探讨早期阿尔茨海默病(AD)脑白质变化与认知功能改变的关系.方法 对14例早期AD患者(AD组)和18名健康老年人(ON组)在1.5 T MR扫描仪上进行扩散张量成像(DTI)扫描.在9个感兴趣区测量并比较各向异性分数(FA)和平均扩散系数((-D)).对2组研究对象进行8个标准的神经心理测试,以评价其基本认知能力状态,并对测试结果 进行比较.分析所有研究对象DTI的FA和(-D)测量结果 与神经心理测试评分的相关性.结果 与ON组相比,AD患者在胼胝体压部(分别为0.25±0.03和0.49±0.03)和后顶-颞叶(分别为0.30±0.02和0.28±0.01)FA降低(t值分别为2.481、1.991,P值均＜0.05)、在胼胝体压部D提高(t=1.751,P＜0.05).在8个神经心理行为测试中,AD患者的评分均低于ON组(t值2.803～4.691,P值均＜0.05).相关性研究结果 显示,AD患者胼胝体压部和后顶-颞叶的FA与多个神经心理测试评分呈正相关(r值0.355～0.499,P值均＜0.05),而在较分散的多个部位(-D)与多个神经心理测试评分呈负相关(r值-0.518～-0.350,P值均＜0.05).结论 在AD早期阶段,患者不仅有认知功能的改变,而且还有白质结构的变化,两者存在一定的相关性,表现为脑白质的选择区域性损害,这种损害反映了AD病理机制中皮质间联系的丢失.

Correlation between white matter alterations and cognitive function decline in early Alzheimer's disease

Objective To investigate the effects of early stage Alzheimer's disease(AD)on white matter(WM)integrity using diffusion tensor imaging(DTI)and its relationship with cognitive function decline.Methods DTI was performed in 32 subjects,including 14 early AD patients and 18 elder controls(ON)with a 1.5 T MR scanner. Fractional anisotropy(FA)and mean diffusivity(-D)values were computed and compared for 9 regions of interest(ROI).Eight standard neuropsychological tests were performed and compared between AD and ON to evaluate basic cognitive capacities of AD.Correlation analysis was applied between FA,(-D) values and scores of neuropsychological tests for all subjects.Results FA significantly decreased in splenium of the corpus callosum and the posterior parietal-temporal region(S2),and D significantly increased in the splenium in AD patients(P＜0.05).AD patients showed lower scores compared with ON in all neuropsychological tests(P＜0.05).FA of the splenium and S2 positively correlated with several tests scores,while (-D) of multiple ROIs negatively correlated with several tests scores (P＜0.05).Conclusions In the early stage of AD,neuropathology has effect not only on cognitive function,but also on white matter structure,and they have strong relationship.AD patients show white matter changes in specific regions,which reflect loss in cortico-cortical connections.