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Poster Slam Session B, Tuesday, August 20, 2019, 3:00 – 3:15 pm, Finlandia Hall, Angela Grant

Brain tumors in left frontal regions impact language laterality as determined by pre-surgical fMRI

Monika Polczynska1, Lilian Beck1, Taylor Kuhn1, Kevin Japardi1, Christopher Benjamin2, Timothy Ly1, Susan Bookheimer1;1University of California, Los Angeles, 2Yale University

Assessing hemispheric dominance before brain surgery is an important guide in surgical planning that can minimize the occurrence of new, surgically-induced language impairments (Kundu et al., 2013). Language dominance can be assessed with the Laterality Index (LI) measure. In functional magnetic resonance imaging (fMRI), LI quantifies information from blood oxygen-level dependent (BOLD) activation in language tasks in each cerebral hemisphere, or in selected regions of interest (ROI) (Benjamin et al. 2018). Generally, individuals with more language activation in the left hemisphere have higher language LI, while individuals with more bilateral language activity have lower language LI. We address the following two questions: (1) Does a brain tumor in different parts of the language system impact the stability of LI differently?, and (2) Are changes in LI due to a decrease in functional activation around the lesion or an increase in activation in brain areas on the contralateral side? We accessed a database of over 1100 patients to perform exact matching. We divided our subjects (n=60; 25 females; 18 left-handed and four ambidextrous; average age=47 years, SD=14.1) into four tumor groups with 15 subjects per group: 1. Left anterior hemisphere, 2. Left posterior hemisphere, 3. Right anterior hemisphere, and 4. Right posterior hemisphere. Patients from groups 1 and 2 were our target sample, with brain tumors within the language regions of the left dominant hemisphere. Groups 3 and 4 served as controls, with tumors within the right language homologs. There were both low- and high-tumor grade patients in each group. We matched the patients based on significant factors that are known to affect LI: tumor location and volume, gender, handedness, and age. We evaluated LI in three language tasks during pre-operative fMRI: object naming, verbal, and auditory responsive naming. We calculated active voxel counts in each hemisphere, and four ROI: Broca’s area, Wernicke’s area, and their right hemisphere homologs. We found that patients with a brain tumor in the left anterior hemisphere had lower language laterality than patients with a brain tumor in the right anterior hemisphere based on active voxel counts in each hemisphere (p=0.020). Evaluating LI in specific ROI enabled us to observe that the left anterior patients had decreased language laterality in Broca’s area (p=0.020) but not in Wernicke’s area. Further, compared to the three other groups, these patients displayed lower active voxel counts in Broca’s area and higher voxel counts in the right hemisphere homolog of Broca’s area. To conclude, a brain tumor located in the left anterior hemisphere affected the stability of language LI. Specifically, patients with a left anterior tumor had less activity in the left frontal language regions (Broca’s area) and elevated activity in the contralateral areas. An important clinical implication of this study is that in patients with brain tumors in the left anterior hemisphere, it is essential to assess language LI using an ROI approach, specifically in the posterior language areas.

Themes: Disorders: Acquired, Language Production
Method: Functional Imaging

Poster B4

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