Neural substrates of aphasia in acute left hemispheric stroke using voxel-based lesion-symptom brain mapping

Abstract

Background: An acquired communication disorders, characterized by an impairment of language modalities, are most often caused by sequelae of stroke. The theory about brain lesions related to aphasia has well reported. However, it is unclear how these brain lesions fit into the language processing in acute stroke. In this study, we aimed to investigate neuroanatomical lesion related to language processing in acute post-stroke patients with left hemispheric lesion using voxel-based lesion-symptom mapping. Methods: This retrospective study included 73 patients with acute first-ever stroke from January 2011 to April 2016. Magnetic resonance images (MRIs) of the brain and evaluation of aphasia using Korean version of the Western Aphasia Battery (K-WAB) were conducted within 1 month after stroke onset. Regions of interests (ROIs) were aligned manually at each affected slice of T1 weighted image with monitoring corresponding FLAIR and diffusion images to confirm plausibility of infarction. Normalization of ROIs and voxel-based statistical analysis have been done using Statistical Parametric Mapping 12 running under Matlab. The K-WAB assessment was included aphasia quotient (AQ), scores of four subtests. Each voxel, lesioned or non-lesioned, was compared with AQ and subtest scores as dependent variable. Results: In our consecutive 73 subjects, 58 patients (79.5%) were verified to be less than 92.8 in AQ. In subgroup analysis, aphasia group showed significantly much more involvement of extra-nuclear area, insula, inferior frontal gyrus and superior temporal gyrus compared to non-aphasia group (p < 0.01). Voxel-based lesion symptom mapping of significant association between brain lesions and the score of spontaneous speech domain was shown in inferior parietal lobule, inferior and middle frontal gyrus and insula. The lesion of insular cortex, inferior parietal lobule, inferior frontal gyrus, middle frontal gyrus and superior temporal gyrus were correlated with score of comprehension subtest. The lesion on inferior parietal lobule, insula, precentral gyrus, inferior frontal gyrus, BA 41 and 22 were correlated with score of repetition subtest. The lesion on inferior parietal lobule, insula and inferior frontal gyrus were correlated with score of naming (p < 0.001, false recovery data corrected). Conclusion: In this study, it is possible to localize the brain lesion related to language processing using voxel-based lesion-symptom analysis from early MRI imaging study in acute stroke. It may be useful to understand the language process and brain lesion after stroke.