Atrophy, hypometabolism and white matter abnormalities in semantic dementia tell a coherent story
Atrophy, hypometabolism and white matter abnormalities in semantic dementia tell a coherent story
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DOI：
10.1093/brain/awr119
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发表时间：
2011-07-01
期刊：
影响因子：
14.5
通讯作者：
Nestor, Peter J.
中科院分区：
文献类型：
--
作者：
Acosta-Cabronero, Julio;Patterson, Karalyn;Nestor, Peter J.
语义性痴呆，语义知识的进行性退化，与局灶性，典型的不对称，颞叶退化有关。腹侧颞叶受影响最严重，萎缩与代谢活性降低具有一致性。在这项研究中，我们使用f -18氟脱氧葡萄糖正电子发射断层扫描和解剖磁共振图像证实了这一说法的真实性。然而，主要目的是通过研究白质变化的全面程度来了解颞叶前部前部皮层病变对神经元投射的影响，而没有对相关束的性质或空间位置进行先验假设。使用一种无偏倚的体素方法，即基于束的空间统计，我们比较了10名轻度/中度语义性痴呆患者和21名匹配对照组的全脑扩散张量成像结果——轴向、径向和平均扩散的绝对指标以及分数各向异性。语义性痴呆患者的绝对扩散度增加和分数各向异性降低的分布在空间上是一致的。所有指标的异常均在统计上具有高度显著性，左侧颞叶前部的白质异常更为极端，因此与灰质的结构和功能成像结果密切匹配。最敏感的变化标志是径向扩散。局部白质束异常向额叶和背侧延伸至颞上和边缘上回。为了检查更多的远程变化，我们进行了骨骼化概率神经束造影分析-在健康对照组中“播撒”患者组中确定为异常的吻侧颞体素。三个主要的神经通路从这个“种子区”发出：钩状、弓形和下纵束。在不太保守的阈值下，语义性痴呆组的张量异常映射到远超过吻侧颞叶的钩状束和弓形束的束束造影；这与下纵束的情况不同，语义性痴呆的异常不会延伸到尾侧的萎缩/低代谢区。研究结果提供了直接的证据，证明了被认为是导致语义痴呆中语义知识恶化和与“经典”语言区域分离的腹侧颞叶损伤是如何与这些语言区域的传出白质投影退化相关的。
Semantic dementia, in which there is progressive deterioration of semantic knowledge, is associated with focal, typically asymmetric, temporal lobe degeneration. The ventrorostral temporal lobe is most severely affected and there is concordance between atrophy and reduced metabolic activity. In this study, we confirmed the veracity of this claim using F-18-fluorodeoxyglucose positron emission tomography and anatomical magnetic resonance images. The principal aim, however, was to understand the impact on neuronal projections from the ventrorostral temporal cortex lesion by studying the full extent of white matter changes, with no a priori assumptions about the nature or spatial location of the tracts involved. Using an unbiased voxel-wise approach known as tract-based spatial statistics, we compared results of whole-brain diffusion tensor imaging-absolute metrics of axial, radial and mean diffusion as well as fractional anisotropy-from 10 patients with mild/moderate semantic dementia and 21 matched controls. Distributions of increased absolute diffusivity and reduced fractional anisotropy for patients with semantic dementia were spatially concordant with each other. Abnormalities in all metrics were highly statistically significant in ventrorostral temporal white matter, more extreme on the left side, thus closely matching results from structural and functional imaging of grey matter. The most sensitive marker of change was radial diffusion. Local white matter tract abnormalities extended rostrally towards the frontal lobe and dorsocaudally towards the superior temporal and supramarginal gyri. To examine more remote changes, we performed a skeletonized probabilistic tractography analysis-'seeding' the rostral temporal voxels identified as abnormal in the patient group-in a healthy control group. Three major neural pathways were found to emanate from this 'seed region': uncinate, arcuate and inferior longitudinal fasciculi. At a less conservative threshold, tensor abnormalities in the semantic dementia group mapped onto the tractographies for the uncinate and arcuate bundles well beyond the rostral temporal lobe; this was not the case for the inferior longitudinal bundle, where abnormalities in semantic dementia did not extend caudal to the atrophic/hypometabolic zone. The results offer direct evidence for how the ventrorostral temporal lesion, proposed to be responsible for deteriorating semantic knowledge in semantic dementia and separate from 'classic' language areas, is associated with degeneration of efferent white matter projections to such language areas.