Structural gray matter changes in primary progressive aphasia variants

Background: Primary progressive aphasia (PPA) is a rare neurodegenerative disease with high clinical, genetic and pathomorphological heterogeneity that greatly complicates its diagnosis. Voxel-based morphometry (VBM) can be used to objectively assess structural gray matter changes and determine atrophy patterns of PPA variants, which can improve the diagnosis of the disease and our understandings of its pathogenesis. Aims: The aim of our work was to evaluate the patterns of atrophy in each of the PPA variants in comparison with the control group. Materials and methods: Patients with a diagnosis of one of the PPA variants, established in accordance with the current diagnostic criteria, were included in the main group. The control group consisted of healthy volunteers without any neurological symptoms and structural brain changes according to MRI. All participants underwent brain MRI, obtained images were processed and used for VBM. VBM was performed with a comparison of gray matter volume between each of the PPA variants and the control group. The study was adjusted for gender, age, and intracranial volume of the participants. Results: 25 patients with nonfluent (nfvPPA), 11 - semantic (svPPA), and 9 - logopenic (lvPPA) PPA variants and 20 healthy volunteers were included in the study. The VBM showed that there is a specific atrophy pattern in each of the PPA variants with predominant involvement of the frontal and insular lobes in nfvPPA, the temporal lobe and hippocampus in svPPA, and a more diffuse frontotemporal pattern in lvPPA. Conclusions: The study revealed gray matter atrophy patterns specific to each of the PPA variants. Obtained results mainly correspond to the clinical presentations of the disease. At the same time, some findings (e.g. absence of the posterior perisylvian atrophy in lvPPA as well as reduced gray matter volume of the orbitofrontal cortex and cerebellum in nfvPPA, premotor cortex, precentral and inferior frontal gyrus in svPPA, and motor cortex in lvPPA) do not correlate with the usual understanding of PPA pathogenesis and require further study.