Structural gray matter changes in primary progressive aphasia variants

BACKGROUND: Primary progressive aphasia is a rare neurodegenerative disease with high clinical, genetic, and pathomorphological heterogeneity that greatly complicates its diagnosis. Voxel-based morphometry can be used to objectively assess structural gray matter changes and determine atrophy patterns in variants of primary progressive aphasia, which can improve the diagnosis and our understanding of its pathogenesis.

AIMS: This study aimed to evaluate the patterns of atrophy in each of the primary progressive aphasia variants in comparison with the control group.

MATERIALS AND METHODS: Patients diagnosed with one of the primary progressive aphasia 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 or structural brain changes. All participants underwent brain magnetic resonance imaging. The obtained images were processed and used for voxel-based morphometry, which was performed by comparing the gray matter volume between each of the primary progressive aphasia variants and the control group. The study was adjusted for the sex, age, and intracranial volume of the participants.

RESULTS: The study enrolled 25 patients with nonfluent, 11 with semantic, and 9 with logopenic variants of primary progressive aphasia, as well as 20 healthy volunteers. Voxel-based morphometry showed a specific atrophy pattern in each of the variants of primary progressive aphasia, with predominant involvement of the frontal and insular lobes in nonfluent, temporal lobe and hippocampus in semantic, and a more diffuse frontotemporal pattern in logopenic variants.

CONCLUSIONS: The study revealed gray matter atrophy patterns specific to each variant of primary progressive aphasia. The obtained results mainly correspond to the clinical presentations of the disease. Moreover, some findings (e.g., absence of the posterior perisylvian atrophy and reduced motor cortex volume in the logopenic variant, atrophy of the orbitofrontal cortex and cerebellum in the nonfluent variant, and premotor cortex, precentral, and inferior frontal gyrus degeneration in the semantic variant) do not correlate with the usual understanding of primary progressive aphasia pathogenesis and require further study.