gms | German Medical Science

Objective: The anatomical location of language is highly variable across individuals. The location of language can be identified cortically using navigated repetitive transcranial magnetic stimulation (nrTMS) and subcortically using diffusion tensor imaging fiber tracking (DTI FT). This study investigates how nrTMS-based cortical locations of language function and DTI FT tractographies of language-eloquent subcortical pathways differ between various languages.

Methods: We included 40 patients with language-eloquent brain lesions speaking various languages. Preoperative nrTMS using an object-naming task identified language-related brain sites. nrTMS-based DTI FT visualized subcortical language tracts. Cortical language error rates and subcortical language pathway volumes were compared between Slavic and Indo-Germanic languages within bilingual patients.

Results: Error rates related to stimulations in the mSFG, pMFG, mPoG, pSFG, and pSTG differed significantly between Slavic and Indo-Germanic languages. Error rates related to stimulations in the pSTG, pMTG, mSFG, trIFG, mMFG, vPoG, and anG differed significantly between bilingual individuals. No differences were found in the subcortical language pathway volumes between Slavic and Indo-Germanic languages nor between bilingual patients. The subcortical language pathway volumes correlated moderately with error rates related to stimulations in the opIFG, mMFG, mSFG, PrG, SMG, dPoG, mSTG, pMTG, and anG in Slavic and Indo-Germanic languages.

Conclusion: Even though the underlying subcortical structure may be similar across languages, there are significant differences in the pattern of cortical location of language between various languages depending on the semantic processing. This is important for indication but also the resection of language-eloquent brain lesions since the location of language cannot be generalized across languages or individuals.