Language impairments and their neuroanatomical correlates in patients after brain tumor resection

The project focused on linguistic and brain mechanisms of language impairments and their dynamics in patients undergoing a resection of a brain pathology. For the first time, the modern linguistic apparatus and relevant neuroscientific methods were used to investigate the language status of a large cohort of patients with brain tumors in preoperative, acute and chronic postoperative periods. In 2018-2020, the data of 60 patients with brain tumors have been collected: all were tested with the Russian Aphasia Test (RAT) and scanned with MRI before and right after surgery; 26 were also tested in the chronic postoperative period. Localization of brain pathologies is presented in Fig. 1.

Fig. 1. Overlay of brain pathologies in the tested cohort of patients.

The analysis of their performance on RAT showed significant difference in the pre- and postoperative language scores: a part of the tested cohort of patients experienced linguistic problems at various linguistic levels and in both comprehension and production after the surgery. That deficit, however, largely regressed in the chronic period. Critically, the observed language impairments differed from the classic post-stroke aphasia syndromes: scores on the RAT subtest tapping into different linguistic levels and modalities correlated, and there was no specific underlying deficit found. Thus, language problems in the neurosurgery population can be classified as ‘mild global aphasia’.

The language data were further used in the MRI analysis. Voxel-based lesion-symptom mapping revealed the involvement of the left middle part of the superior temporal gyrus, the temporal pole and the posterior inferior frontal cortex in transient postoperative comprehension problems (see Fig. 2). Transient production impairments were found related to the resection of the left posterior inferior frontal and insular cortices (see Fig. 3). Permanent impairments of naming were associated with postoperative damage of the left temporal pole, while discourse production problems were related to the supplementary motor region. These results conform to modern models of language neuroanatomy extending beyond the classic Broca and Wernicke areas.

Fig. 2. VLSM of language comprehension in the acute postoperative period.

Fig. 3. VLSM of language production in the acute postoperative period .

The reconstruction of long associative white-matter pathways revealed that postoperative impairment of comprehension was associated with the resection of left ventral tracts (inferior frontal-occipital, inferior longitudinal, uncinate fasciculi), but also with damage to the left arcuate fasciculus, which has been traditionally associated with language production. Additionally, resection of the left inferior frontal-occipital fasciculus resulted in language production difficulties. These pinpoint the critical role of both long associative pathways linking distant brain regions (the dorsal – arcuate fasciculus and the ventral – inferior frontal-occipital fasciculus) in the left hemisphere for both language comprehension and production. Finally, the volumetric morphometry analysis showed the gray matter increase in the cingulate cortex of the right hemisphere as a function of improved language status in the chronic postoperative period. This suggests the significant contribution of the contralateral hemisphere for language reorganization in the neurosurgery population – in particular, regions involved in learning and memory.

This suggests the significant contribution of the contralateral hemisphere for language reorganization in the neurosurgery population. The results of the project, which are largely new, significantly add to the understanding of the language status in neurosurgery patients at different stages of their treatment and the neuroanatomical changes underlying it.

Representing papers :

1.  Zyryanov et al. (2019). The contributions of the arcuate fasciculus segments to language processing: Evidence from brain tumor patients.Russian Journal of Cognitive Science, 6 (1), 25-37.

2.   Dragoy et al. (2019). ‘A moderate global aphasia’: the pattern of language deficits in acute post-surgical tumor patients. Stem-, Spraak- en Taalpathologie  24, Supplement, 66-68.

The project was supported by RFBR grant № 18-012-00829 (2018-2020), PI - Olga Dragoy

Implemented in collaboration with theNational Medical Surgery Center named after N.I. Pirogov and N. N. Burdenko National Medical Research Center of Neurosurgery.