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Subcortical lesions in the left middle temporal gyrus are associated with increased overall severity of aphasia
Poster Session E, Sunday, September 14, 11:00 am - 12:30 pm, Field House
Shinya Uchida1,2, Takuya Nakayama2, Rio Uchiyama2, Masaki Sugiyama2, Marta Pijanowska3, Masao Nagayama2, Toshiyuki Fujiwara1; 1Juntendo University, 2International University of Health and Welfare, 3Rikkyo University
[Introduction] Aphasia affects multiple domains of language, including auditory comprehension, speech, repetition, reading, and writing. While lesions in widespread areas of the left hemisphere can lead to aphasia, the severity of impairment in each language domain varies among individuals. The overall severity of aphasia is a useful index to represent the extent of language dysfunction across multiple domains. However, the critical brain regions that influence the overall severity of aphasia are not yet fully understood. The aim of the present study is to identify brain regions associated with the overall severity of aphasia using voxel-based lesion-symptom mapping (VLSM) analysis. [Methods] Participants were patients registered between 2016 and 2024 at the associated hospital. Inclusion criteria were defined as follows: patients were diagnosed with aphasia, the underlying disease causing aphasia was their first ischemic or hemorrhagic stroke, the lesion was restricted to the left hemisphere, and language test results were available. A total of 39 aphasic patients were included. The Standard Language Test of Aphasia (SLTA) was used as the language test, and the overall severity of aphasia for each participant was assessed using the SLTA general score, where a lower score indicates greater severity. For patients who underwent the SLTA multiple times during the therapy, the most recent score was used for analysis. A lesion mask image for each patient was created on the standard brain template (MNI152) using MRIcroGL software. All lesion mask images were visually confirmed by a certified neurologist. To explore brain regions affecting the severity of aphasia, VLSM analysis was conducted using NiiStat software. In the analysis, the following variables were used as covariates: the number of days from birth to the SLTA examination, the number of days from disease onset to the SLTA examination, and lesion volume. Voxels in which at least four patients had lesions in the left hemisphere were analyzed. The significance threshold in the VLSM analysis was set at P < .05 (corrected using the Freedman-Lane permutation test). Finally, neural fiber connections with the voxels identified by the VLSM analysis were estimated using BCBToolKit software. [Results] The participants’ mean age was 76.6 (SD = 10.2). Their mean SLTA general score was 6.7 (SD = 3.0; range: 0–10). VLSM analysis showed that lesions in subcortical regions of the left middle temporal gyrus significantly increased the overall severity of aphasia. Voxels identified by the VLSM analysis showed dorsal and ventral neural fiber tracts extending into the frontal and parietal lobes. [Discussion] Previous studies associated lesions in the left middle temporal gyrus with auditory comprehension disorder (Bates et al., 2004). The findings of the present study, which demonstrated associations between lesions in subcortical regions of the left middle temporal gyrus and greater overall severity of language impairments, may primarily reflect deficits in auditory comprehension caused by damage to this region. Additionally, such damage may disrupt not only language comprehension but also speech, repetition, reading, and writing due to disconnection between this region and other language-related areas in the frontal and parietal lobes.
Topic Areas: Disorders: Acquired,