Abstracts

Preserving eloquent cortical areas is a central goal of pre-surgical evaluation in localized epilepsy. While left hemisphere dominance is typical for language processing, bilingual patients are more likely to exhibit atypical language organization. Left hemisphere dysfunction can trigger neural reorganization, shifting language functions to the right hemisphere. Key factors such as language acquisition, level of bilingualism, age of seizure onset, seizure burden, and the functional and emotional roles of each language must be considered. Heritage languages, even when not used daily, are critical for maintaining cultural identity and family bonds, which impacts social-emotional well-being. This case series illustrates diverse outcomes in functional language use and neuroanatomical organization, underscoring the need for bilingual language mapping to assess surgical risk in bilingual patients.

We reviewed 9 bilingual (Spanish/English) epilepsy patients with varying bilingualism levels and seizure onset zones. Neuropsychological evaluations confirmed both languages were functional or of heritage value. Functional magnetic resonance imaging (fMRI) and/or magnetoencephalography (MEG) were used to clarify language lateralization and assess surgical risks associated with atypical language representation.

 Bilateral recruitment for language processing was seen in 5 out of 9 cases, without clear links to second language proficiency (2/3 high, 3/6 low), age of acquisition (3/5 early, 2/4 late), seizure focus (2/4 left, 3/5 right), or age of seizure onset (2/4 adolescent, 3/5 early development). Presurgical workup (fMRI/MEG) was typically done in one language (7/9); 2 of 3 balanced bilinguals were tested in both languages, while 1 was tested in English only. Non-balanced bilinguals were tested only in their dominant language. In 5 cases, neuropsychological findings were inconsistent with expected deficits based on epilepsy focality, with 3 of these showing bilateral language representation.

This case series highlights the complexity of language representation in bilingual epilepsy patients. As has been established in the literature, divergence of language networks in bilingual patients is the standard and not the exception. Limitations of language mapping in only one language (even when that is the “dominant” language) are demonstrated here. Patients with right hemisphere pathology and seemingly left-lateralized language still face significant risk for language deficits if the right hemisphere participates in language processing. The role of heritage languages in cultural identity and psychosocial well-being must not be overlooked. Thus, we recommend thorough clinical interview regarding bilingual language history, potential neuropsychological testing in both languages, and comprehensive language lateralization / localization in each language. In many cases, further bilingual language mapping (sEEG) may be needed prior to surgery to ensure optimal preservation of linguistic abilities.