Abstract: Objective  Using diffusion tensor imaging (DTI) to explore the microstructure changes of white matter in subcortical ischemic vascular cognitive impairment (SIVCI) and its correlation with cognitive function.  Methods  Forty-nine patients with subcortical ischemic cerebrovascular diseases were collected. By using Clinical Dementia Rating Scale (CDR), they were classified into 10 cases of vascular dementia (VaD group), 20 cases of vascular cognitive impairment-no dementia (VCIND group) and 19 cases of normal cognitive function (control group). Conventional MRI and DTI were performed in all cases. Based on the DTI data, voxel-based analysis was used to assess the whole brain region. Correlation analysis was applied to illustrate the relationship between DTI parameters and cognitive scale in VaD patients.  Results  Compared with the control group, fractional anisotropy (FA) values of patients in VaD group decreased in medial prefrontal cortex, anterior cingulate cortex, corpus callosum stem, bilateral parietal lobes, right temporal lobe and bilateral orbitofrontal lobes (P = 0.000, for all), and FA values of patients in VCIND group decreased in right inferior frontal gyrus, right hippocampus and bilateral precuneus (P = 0.000, for all). Compared with VCIND group, FA values of patients in VaD group decreased in medial prefrontal cortex, anterior cingulate, corpus callosum, bilateral parietal lobes and right temporal lobe (P = 0.000, for all). Compared with the control group, mean diffusivity (MD) values in VaD group increased in medial prefrontal cortex, corpus callosum, bilateral parietal lobes, bilateral temporal lobes and anterior cingulate (P = 0.000, for all), while in VCIND group increased in bilateral precuneus and right hippocampus (P = 0.000, for all). Compared with VCIND group, MD values in VaD group increased in right medial prefrontal cortex, anterior cingulate cortex, corpus callosum stem, bilateral parietal lobes and bilateral temporal lobes (P = 0.000, for all). The correlation analysis showed that the FA value of medial prefrontal lobe in VaD group was negatively correlated with the time to finish Trail Making Test A (TMT-A; r = - 0.782, P = 0.007), and MD value of bilateral inferior frontal gyrus was positively correlated with the time to complete TMT-A (r = 0.877, P = 0.001).  Conclusions  DTI was more sensitive on the white matter microstructure change of SIVCI patients than conventional MRI. It can reflect patient's early cognitive functional changes. Microstructrual change in medial prefrontal white matter is an important factor which may influence the executive functions of patients with SIVCI. 

Key words: Cognition disorders, Dementia, vascular, Brain ischemia, Cerebral cortex, Neuropsychological tests, Magnetic resonance imaging

摘要： 目的 通过扩散张量成像（DTI）探讨皮质下缺血性血管性认知损害患者白质微结构变化及其与认知功能之间的相关性。方法 采集49 例皮质下缺血性脑血管病患者［轻度血管性痴呆（VaD）10 例、非痴呆型血管性认知损害（VCIND）20 例、认知功能正常19 例］DTI 数据并观察皮质下白质微结构改变，分析VaD 组患者DTI 参数与认知功能间的相关性。结果 与对照组相比，VaD 组内侧前额叶、前扣带回、胼胝体干、双侧顶叶、右侧颞叶、双侧眶额叶，以及VCIND 组右侧额下回、右侧海马、双侧楔前叶FA 值减低（均P = 0.000）；与VCIND 组比较，VaD 组内侧前额叶、前扣带回、胼胝体、双侧顶叶、右侧颞叶FA 值减低（P = 0.000）。与对照组相比，VaD 组内侧前额叶、胼胝体、双侧顶叶、双侧颞叶、前扣带回，以及VCIND 组双侧楔前叶、右侧海马MD 值升高（均P = 0.000）；与VCIND 组相比，VaD 组右侧内侧前额叶、前扣带回、胼胝体干、双侧顶叶、双侧颞叶MD 值升高（均P = 0.000）。VaD 组内侧前额叶FA 值与数字连线测验A 时呈显著负相关（r = - 0.782，P = 0.007），双侧额下回MD 值与数字连线试验A 时程呈显著正相关（r = 0.877，P = 0.001）。结论 DTI对皮质下缺血性认知损害患者白质微结构改变更敏感，能够反映患者认知功能早期异常改变；内侧前额叶白质微结构的改变是影响患者执行能力的重要因素。

关键词: 认知障碍, 痴呆, 血管性, 脑缺血, 大脑皮质, 神经心理学测验, 磁共振成像