Functional MRI for bilingual epilepsy surgery patients: serving a diverse pediatric cohort

Objective: Functional MRI (fMRI) helps with the identification of eloquent cortex to assist with function preservation in patients who undergo epilepsy surgery. Language and memory tasks can even be used effectively in clinically involved pediatric patients. Most pediatric studies report on English speaking-only cohorts from English-dominant countries, yet languages other than English (LOEs) are increasingly prevalent in countries such as the US. This study evaluated the efficacy of pediatric fMRI for primarily bilingual patients with LOEs undergoing epilepsy surgery workups.

Methods: The authors reviewed patients who underwent epilepsy surgery workup at Seattle Children's Hospital and identified all patients who had valid verbal fluency fMRI tasks from 2007 to 2021, including the bilingual and LOE patients within this cohort who had LOE fMRI language scans. The percentage of LOE-bilingual patients and the LOEs were identified, and the LOE versus English activation in bilingual patients was compared.

Results: Of the 363 patients with epilepsy surgery workup who had successful verbal fluency fMRI tasks during 2007-2021, 63 (17%) were bilingual or LOE-only patients and 300 were monolingual English-language patients. Of the 63 patients, 18 were bilingual and had LOE plus English scans; 3 patients were fluent only in one non-English language and thus underwent LOE scans only; 30 were bilingual but chose to have only English language scans; and 12 additional patients had limited or questionable LOE proficiency and underwent English-only scans. Sixteen of 18 bilingual scans allowed reliable calculation for the language-related region of interest (ROI), and this study focused on the comparison of the first language and second language Broca's area and Wernicke's area ROI measurements. All patients had activation in both languages, with 100% concordance in terms of laterality for Broca's area ROIs and 94% concordance for Wernicke's area ROIs. However, while lateralization indices were largely concordant, variability in exact areas and extent of activation was noted.

Conclusions: This preliminary pediatric study suggests that language fMRI tasks can be completed effectively with bilingual and LOE pediatric patients as part of epilepsy surgery workups, regardless of the language spoken by the patient. Individual patient LOE and English activations were generally concordant in terms of lateralization, although exact areas of activation varied. Important future steps need to include larger samples, better pre-fMRI evaluation of bilingual proficiency, and standards for fMRI assessments with a diversity of patients, particularly bilingual pediatric patients.