Work

Tumor lesions in the supplementary motor area may induce large-scale sensorimotor and cognitive network alterations— A functional and structural connectivity analysis

Year: 2026

Type: article

Abstract: Background Patients with brain tumors involving the SMA often develop postoperatively a mostly transient contralateral akinesia (‘SMA-syndrome'), which may primarily be a cognitive disorder of executive functions. However, the neurophysiological correlates are unclear. Considering the SMA as a gateway between motor and cognitive control functions, we explored structural SMA-connectivity (SC), and functional connectivity (FC) of the sensorimotor (SMN), and of cognitive networks in SMA-tumor patients. Methods 13 SMA-tumor patients and 13 matched healthy controls underwent diffusion-tensor-imaging (DTI) and resting-state-fMRI preoperatively. Intra- (Frontal Aslant Tract) and interhemispheric SC of the SMA (SMA-SMA, SMA-M1) was compared between groups. FC-networks were established by group Independent Component Analysis (ICA), and subjected to a second-level ROI-to-ROI (region-of-interest) analysis to investigate between-group differences. Results DTI revealed microstructural white-matter disintegration and smaller tract volumes of SMA-M1 connectivity ( p < 0.005), and by trend of the FAT ( p < 0.06), with differing SMA-M1 fiber-length in patients ( p < 0.026). SMA-SMA SC was not reduced, but showed greater variance in patients. While FC was significantly decreased within different cognitive networks, FC was increased within the SMN, as well as between the SMA and the contralesional frontoparietal network ( p < 0.046) in patients. Conclusions In this exploratory study, we found sensorimotor- as well as large-scale cognitive network alterations prior to therapeutic intervention, suggesting tumor-associated SC disintegration to be accompanied by in- and decreases of FC within and across different networks. Future studies incorporating neuropsychological-testing are required to characterize pretherapeutic connectivity alterations with regard to their behavioral significance, and to determine whether they may impact the postoperative functional outcome.

Source: Frontiers in Neurology

DOI: 10.3389/fneur.2026.1878278