Abstracts

Rationale: Determination of language laterality is integral to surgical planning in refractory epilepsy cases. Extant research has shown language migrates to the non-dominant hemisphere in response to left-sided lesions. Limited knowledge of language compensation, which is likely multifaceted, presents complications when assessing language laterality. This study aimed to examine 1) the effect of MTS on distribution of language dominance and 2) the relationship between performance on neuropsychological language measures and language dominance as determined by fMRI in patients with temporal lobe epilepsy. Methods: Retrospective data on fMRI and neuropsychological tests was compiled on patients with refractory epilepsy undergoing interdisciplinary pre-surgical workup (N=93) with mean age of 37.01 (SD = 12.17) and mean education of 12.51 (SD = 3.27). The sample was stratified by non-lesional with varying laterality of seizure foci (N=48), right MTS (N=19), and left MTS (N=26). Language dominance was determined by voxelwise analysis of task-based functional Magnetic Resonance Imaging (fMRI) and was further stratified into unilateral, mixed bilateral, and pure bilateral language groups. Results were compared to performance on Boston Naming Test; BNT, Phonemic Verbal Fluency; FAS, and Categorical Verbal Fluency (CVT, Animals). Results: Statistical analyses showed robust unilateral left language dominance (N = 17, 89.5%) and diminished presentation of bilateral language (N = 1, 5.3%) in patients with right MTS. Interestingly, similar frequencies of bilateral language distribution were found within the left MTS (N = 10, 38.4%) and non-lesional groups (N = 14, 29.2%). Additionally, language dominance and T-scores for CVT were negatively correlated within the left MTS group (rs = -.76, p = .02); whereas, BNT and FAS were not significantly correlated with language dominance. There were no significant correlations found between language dominance and the aforementioned neuropsychological language measures in the right MTS or non-lesional groups.  Conclusions: Patients with left MTS and non-lesional epilepsy demonstrated an almost identical rate of bilateral language distribution; whereas, patients, with right MTS showed no language distribution. The findings suggest a robust relationship of bilateral language distribution to epilepsy, independent of MTS. fMRI and language performance results are not correlated in non lesional epilepsy cases. Of the multiple neuropsychological language tests only CVT animals shows correlation to fMRI in patients with left MTS. Further investigation of the relationship between language dominance and seizure focus is needed in order to aid in surgical planning and anticipating cognitive outcomes.  Funding: No funding