Abstract: Objective  To analyze the structural changes of cerebral gray and white matter in patients with semantic dementia (SD), and to promote the knowledge of its pathological changes and mechanisms.  Methods  Sixteen SD patients and 17 normal controls were scanned with a 3.0T MR scanner and the whole brain three?dimensional high-resolution structural images and diffusion tensor imaging (DTI) images were acquired. The gray matter density and fractional anisotropy (FA) values of white matter fiber tracts were analyzed by professional statistical softwares or packages respectively. The statistical analysis of gray matter density and FA values between 2 groups were processed by two sample t test, and the statistical threshold were set as P < 0.001, Voxel > 338 and P < 0.001, Voxel > 103 respectively.  Results  Compared with the healthy controls, SD patients appeared significantly reduced gray matter density in bilateral temporal lobes, particularly in temporal pole. In addition, SD group showed more areas with grey matter loss in the left cerebral hemisphere, including the left inferior temporal gyrus, left supramarginal gyrus, left inferior parietal gyrus and left middle frontal gyrus. SD group also showed an obviously lower FA value in bilateral white matters of temporal lobe, including bilateral uncinate fasciculus, left cingulum (hippocampus) and bilateral fronto-occipital fasciculus. The abnormal areas of gray matter and white matter showed a high consistency in their anatomical connection.  Conclusions  The study helps to reveal the pathological and anatomical basis of semantic dementia, and provides objective evidence for understanding the pathogenesis of semantic dementia.

Key words: Dementia, Frontal lobe, Temporal lobe, Magnetic resonance imaging

摘要： 目的 分析语义性痴呆患者灰质和白质结构变化，提高对其病理改变和发生机制的认识。方法 采用3.0T MRI 扫描仪对16 例语义性痴呆患者和17 例正常对照者进行全脑扫描，扫描序列包括三维高分辨力结构像和扩散张量成像（DTI）。通过专业统计软件分别对全脑灰质密度和白质纤维束部分各向异性（FA）值进行分析，比较两组受试者全脑灰质密度（P < 0.001，Voxel > 338）和白质纤维束FA 值（P < 0.005，Voxel > 103）。结果 与对照组相比，语义性痴呆组患者双侧颞叶，特别是颞极表现为灰质密度显著降低，以左侧大脑半球额颞顶叶灰质密度减低区域更为广泛，包括左侧颞下回、缘上回、顶下回和额中回；同时双侧颞叶白质纤维束FA 值显著降低，包括双侧钩束、左侧扣带（海马）纤维和双侧下额枕束。白质纤维束FA 值分析结果与VBM 法所显示的灰质密度在解剖学上呈现极高的一致性。结论 本研究在体揭示了语义性痴呆的病理学和解剖学基础，为理解语义性痴呆的病理学机制提供了客观佐证。

关键词: 痴呆, 额叶, 颞叶, 磁共振成像