Andreotti Jennifer, Dierks Thomas, Wahlund Lars-Olof, Grieder Matthias
Translational Research Center, University Hospital of Psychiatry, University of Bern, Bern, Switzerland.
Karolinska Institute, Department of Neurobiology, Care Sciences and Society (NVS), Division of Clinical Geriatrics, Stockholm, Sweden.
J Alzheimers Dis. 2017;55(3):981-993. doi: 10.3233/JAD-160571.
The progression of cognitive deficits in Alzheimer's disease and semantic dementia is accompanied by grey matter atrophy and white matter deterioration. The impact of neuronal loss on the structural network connectivity in these dementia subtypes is, however, not well understood. In order to gain a more refined knowledge of the topological organization of white matter alterations in dementia, we used a network-based approach to analyze the brain's structural connectivity network. Diffusion-weighted and anatomical MRI images of groups with eighteen Alzheimer's disease and six semantic dementia patients, as well as twenty-one healthy controls were recorded to reconstruct individual connectivity networks. Additionally, voxel-based morphometry, using grey and white matter volume, served to relate atrophy to altered structural connectivity. The analyses showed that Alzheimer's disease is characterized by decreased connectivity strength in various cortical regions. An overlap with grey matter loss was found only in the inferior frontal and superior temporal areas. In semantic dementia, significantly reduced network strength was found in the temporal lobes, which converged with grey and white matter atrophy. Therefore, this study demonstrated that the structural disconnection in early Alzheimer's disease goes beyond grey matter atrophy and is independent of white matter volume loss, an observation that was not found in semantic dementia.
阿尔茨海默病和语义性痴呆中认知缺陷的进展伴随着灰质萎缩和白质退化。然而，神经元丢失对这些痴呆亚型中结构网络连通性的影响尚未得到充分理解。为了更深入地了解痴呆中白质改变的拓扑组织，我们采用基于网络的方法来分析大脑的结构连通性网络。记录了18例阿尔茨海默病患者、6例语义性痴呆患者以及21名健康对照者的扩散加权和解剖MRI图像，以重建个体连通性网络。此外，基于体素的形态测量学利用灰质和白质体积，用于将萎缩与改变的结构连通性联系起来。分析表明，阿尔茨海默病的特征是各个皮质区域的连通性强度降低。仅在下额叶和颞上区发现与灰质丢失有重叠。在语义性痴呆中，颞叶的网络强度显著降低，这与灰质和白质萎缩相一致。因此，本研究表明，早期阿尔茨海默病中的结构断开超出了灰质萎缩，并且与白质体积丢失无关，这一观察结果在语义性痴呆中未发现。
