The influence of lesion volume, cortex thickness and lesion localization on chronic post-stroke aphasia severity

Background and purpose: At the acute stage of stroke, the aphasia severity depends on lesion volume and its localization. However, at the chronic stage, this correlation becomes vague, and the cortical thickness in the specific brain regions shows more association with the aphasia severity. Methods: We estimated a correlation between speech impairment and brain morphometric data in 15 patients with fluent aphasia after the chronic left hemisphere stroke. Assessment of Speech in Aphasia (ASA) was used to score patient speech comprehension and production. Results: There were no significant correlations of the lesion volume and speech impairments. However, a multi-regression analysis revealed significant negative dependence of ASA scores on the interaction of two factors: lesion volume and difference in thickness of the contralesional and perilesional temporal lobe. Expectedly, the temporal lobe grey matter in the left hemisphere was significantly thinner than in the contralateral hemisphere. The lesion overlap with language-specific Brodmann areas in the temporal and frontal lobes caused greater aphasia severity. Conclusions: Our results provide further evidence that at the chronic stage not only lesion size but also altered thickness of temporal cortex influence the speech function.