IMG-19. Neural correlates of language errors Induced by direct cortical stimulation during awake surgery: cortical and subcortical differences and their implications for oncological resection strategy

BACKGROUND Direct cortical stimulation during awake surgery for gliomas in speech-relevant areas has become standard, offering insight into functional brain networks. This approach has shown improved long-term survival and functional outcomes due to more complete tumor resection in patients with low-grade gliomas. However, a full understanding of language networks that could guide resection and treatment strategies remains lacking. METHODS We analyzed error points from direct cortical stimulation in 58 patients undergoing awake surgery for speech-relevant low-grade gliomas. Error points were categorized into speech and language errors, normalized to MNI space, and assessed for spatial clustering and white matter tract involvement. RESULTS We examined 330 error coordinates, categorized as language (anomia, semantic, phonological) or speech errors (articulation, hesitation, no response). Articulation and no-response errors were predominantly localized in the precentral gyrus (p < 0.001) and frequently associated with disconnection of the arcuate fasciculus not Broca’s region. Language errors were mainly located in the opercular part of the inferior frontal gyrus and superior temporal gyrus and primarily involved the inferior longitudinal fasciculus. Both error types showed a notable component of transcallosal connectivity partly mirroring the cortical regions of left hemisphere. DISCUSSION Our findings support that Broca’s aphasia is more closely linked to arcuate fasciculus disruption than to classical Broca’s area lesions. To our knowledge, the observed strong interhemispheric connectivity in speech errors has not previously been demonstrated in brain tumor patients. These results highlight the importance of fiber tract-based guidance over traditional anatomical landmarks in resecting tumors in speech-eloquent areas, potentially improving both functional preservation and oncologic outcomes.