Assessing naming and verbal memory in bilingual epilepsy: Challenges and insights for surgical planning

Naming and verbal memory are key components of epilepsy evaluations, as impairments often reflect left temporal dysfunction, and baseline performance helps estimate postsurgical risk. The utility of naming tests in bilingual individuals with epilepsy, however, has been questioned. We examined whether naming and verbal memory performance reflects seizure laterality in bilingual adults, how bilingualism affects baseline scores, and whether bilingual factors moderate the effects of seizure laterality on cognition.

We analyzed naming and verbal memory data from 148 monolingual and 63 bilingual adults with unilateral epilepsy across two centers. Participants completed English-based tests of visual naming, story recall, and word-list recall. Analyses of covariance and Bayesian models tested effects of seizure laterality, bilingual status, and their interaction. Regressions tested the moderating effects of bilingual factors (e.g., age at acquisition, proficiency, English immersion).

Bilinguals scored lower on naming than monolinguals, but both groups showed worse naming in left versus right hemisphere epilepsy (nonsignificant interaction). Using monolingual norms, naming impairment was far more frequent in bilinguals (90%-92% left onset, 63%-71% right onset) than monolinguals, but rates normalized after adjusting for the bilingual naming disadvantage. Among non-US-born bilinguals, greater immersion was associated with better naming in right-but not left-hemisphere epilepsy. For verbal memory, seizure laterality effects were present in story recall, and in word-list recall among patients with mesial temporal sclerosis, but did not differ by bilingual status.

Naming and verbal memory remain reliable markers of seizure laterality in bilingual adults with epilepsy. For naming, however, improved measures and bilingual-specific norms are essential to avoid misclassification and support accurate clinical decision-making.