Grey Matter Reshaping of Language-Related Regions Depends on Tumor Lateralization

SIMPLE SUMMARY: Brain tumors have a profound impact on the structural organization of the brain, particularly when located near language-related regions, resulting in impaired language processing. To investigate this phenomenon, we studied high-resolution MRI scans of patients with brain tumors in the left (dominant for language) and right (nondominant for language) hemispheres and compared them to controls. Specifically, we examined the grey matter volume in 10 language-related regions. Our findings demonstrate that brain tumors, regardless of their lateralization induce global volumetric changes in both the affected and contralesional hemispheres. These changes are influenced by the tumor’s lateralization and suggest that the brain undergoes structural reshaping to cope with the language deficits caused by the tumors. This study sheds light on the intricate relationship between brain tumors and language processing and contributes to the understanding of the mechanisms underlying neuroplasticity subsequent to lesion occurrence. ABSTRACT: A brain tumor in the left hemisphere can decrease language laterality as assessed through fMRI. However, it remains unclear whether or not this decreased language laterality is associated with a structural reshaping of the grey matter, particularly within the language network. Here, we examine if the disruption of the language hubs exclusively affects the macrostructural properties of the contralateral homologues or whether it affects both hemispheres. This study uses voxel-based morphometry applied to high-resolution MR T1-weighted MPRAGE images from 31 adult patients’ left hemisphere, which is dominant for language. Eighteen patients had brain tumors in the left hemisphere, and thirteen had tumors in the right hemisphere. A cohort of 71 healthy individuals matched with respect to age and sex was used as a baseline. We defined 10 ROIs per hemisphere involved in language function. Two separate repeated-measure ANOVAs were conducted with the volume per region as the dependent variable. For the patients, tumor lateralization (right versus left) served as a between-subject factor. The current study demonstrated that the presence of a brain tumor generates global volumetric changes affecting the left language regions and their contralateral homologues. These changes are mediated by the lateralization of the lesion. Our findings suggest that functional mechanisms are supported by the rearrangement of the grey matter.