Abstract
The non-fluent/agrammatic variant of primary progressive aphasia (nfvPPA) and semantic variant (svPPA) of frontotemporal dementia (FTD) are neurodegenerative diseases. Previous works have shown alterations of fractional anisotropy (FA) and mean diffusivity (MD) from diffusion tensor images (DTIs). This manuscript is aimed at using DTI images to build a global tractography and to identify atrophy patterns of white matter in each variant. Twenty patients with svPPA, 20 patients with nfvPPA, 26 patients with behavioral variant of FTD (bvFTD) and, 33 controls were included. An analysis based on the connectivity of structural networks showed changes in FA and MD in svPPA and nfvPPA with respect to bvFTD. Much damage in the internal networks of the left temporal lobe was found in svPPA patients; in contrast, patients with nfvPPA showed atrophy in networks from the basal ganglia to motor and premotor areas. Those findings support the dual stream model of speech and language.
Highlights
Primary progressive aphasias (PPAs) are clinical syndromes characterized by a progressive and insidious alteration in speech, grammar, or language [1] comprehension
The clinical differences between all groups are reported in the section on behavioral data and, in the sections that follow, the comparisons between variants of frontotemporal dementia (FTD) based on fractional anisotropy (FA) and mean diffusivity (MD), the networks with significant differences
According to results from a one-way ANOVA test and subsequent post-hoc analyses (Tukey’s HSD) (Table 1), the global cognition measured by the MoCA test showed higher scores at behavioral variant of FTD (bvFTD) than semantic variant of primary progressive aphasia (svPPA) and non-fluent/agrammatic variant of primary progressive aphasia (nfvPPA) (p < 0.05 in both cases)
Summary
Primary progressive aphasias (PPAs) are clinical syndromes characterized by a progressive and insidious alteration in speech, grammar, or language [1] comprehension. The classification based on these three types is supported by clinical characteristics of language disturbances and cerebral pattern atrophy [4]. Disturbances in comprehension and semantic knowledge are the major characteristics of svPPA. Brain atrophy in svPPA was found in temporal lobes bilaterally in anterior and lateral regions. Some reports found greater changes in the left temporal than in the right [8]. The semantic impairment has been associated with hypoperfusion in anterior regions of the left temporal lobe in contrast. Changes in the right hemisphere are related to extending the semantic network [10] and knowledge of self [7]
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