Nigro Salvatore, Tafuri Benedetta, Urso Daniele, De Blasi Roberto, Cedola Alessia, Gigli Giuseppe, Logroscino Giancarlo
Institute of Nanotechnology (NANOTEC), National Research Council, Lecce, Italy.
Center for Neurodegenerative Diseases and the Aging Brain, Department of Clinical Research in Neurology, University of Bari Aldo Moro, Pia Fondazione Cardinale G. Panico, Tricase, Lecce, Italy.
Brain Imaging Behav. 2022 Jun;16(3):1113-1122. doi: 10.1007/s11682-021-00560-2. Epub 2021 Nov 10.
Semantic (svPPA) and nonfluent (nfvPPA) variants of primary progressive aphasia (PPA) have recently been associated with distinct patterns of white matter and functional network alterations in left frontoinsular and anterior temporal regions, respectively. Little information exists, however, about the topological characteristics of gray matter covariance networks in these two PPA variants. In the present study, we used a graph theory approach to describe the structural covariance network organization in 34 patients with svPPA, 34 patients with nfvPPA and 110 healthy controls. All participants underwent a 3 T structural MRI. Next, we used cortical thickness values and subcortical volumes to define subject-specific connectivity networks. Patients with svPPA and nfvPPA were characterized by higher values of normalized characteristic path length compared with controls. Moreover, svPPA patients had lower values of normalized clustering coefficient relative to healthy controls. At a regional level, patients with svPPA showed a reduced connectivity and impaired information processing in temporal and limbic brain areas relative to controls and nfvPPA patients. By contrast, local network changes in patients with nfvPPA were focused on frontal brain regions such as the pars opercularis and the middle frontal cortex. Of note, a predominance of local metric changes was observed in the left hemisphere in both nfvPPA and svPPA brain networks. Taken together, these findings provide new evidences of a suboptimal topological organization of the structural covariance networks in svPPA and nfvPPA patients. Moreover, we further confirm that distinct patterns of structural network alterations are related to neurodegenerative mechanisms underlying each PPA variant.
原发性进行性失语（PPA）的语义变异型（svPPA）和非流利变异型（nfvPPA）最近分别与左额岛叶和颞前区白质及功能网络改变的不同模式相关。然而，关于这两种PPA变异型中灰质协方差网络的拓扑特征，目前所知甚少。在本研究中，我们采用图论方法描述了34例svPPA患者、34例nfvPPA患者和110名健康对照者的结构协方差网络组织。所有参与者均接受了3T结构磁共振成像（MRI）检查。接下来，我们使用皮质厚度值和皮质下体积来定义个体特异性连接网络。与对照组相比，svPPA和nfvPPA患者的标准化特征路径长度值更高。此外，相对于健康对照者，svPPA患者的标准化聚类系数值更低。在区域水平上，与对照组和nfvPPA患者相比，svPPA患者在颞叶和边缘脑区的连接性降低且信息处理受损。相比之下，nfvPPA患者的局部网络变化集中在额叶脑区，如岛盖部和额中回。值得注意的是，在nfvPPA和svPPA脑网络的左半球均观察到局部度量变化占主导。综上所述，这些发现为svPPA和nfvPPA患者结构协方差网络拓扑组织欠佳提供了新证据。此外，我们进一步证实，不同的结构网络改变模式与每种PPA变异型潜在的神经退行性机制相关。
