gms | German Medical Science

Objective: Resting-state functional MRI (rs-fMRI) allows mapping temporally coherent brain networks and intra- and inter-network alterations have been described in different diseases. With regard to gliomas, findings are inconclusive: while both tumor-related increases and decreases in resting-state functional connectivity (RSFC) have been reported, recent studies suggest asymmetries in hemispheric vulnerability of networks. We investigated hemispheric RSFC differences in the Default-Mode and Fronto-Parietal Network (DMN, FPN) between left- and right-hemispheric (LH, RH) gliomas, addressing the role of asymmetry in the effect the tumor might have on network dynamics.

Methods: 27 glioma patients (mean age: 49±17 years, 15 males, 16 LH gliomas, 26 right-handed) and 27 healthy controls (mean age: 46±13 years, 16 males, 26 right-handed) were preoperatively enrolled in the study and underwent anatomical and rs-fMRI as well as neuropsychological assessment. Independent Component Analyses and subsequent permutation tests were performed separately for controls and patients with LH and RH gliomas, respectively, to identify the DMN and FPN. Hemispheric DMN- and FPN-RSFC were computed, compared across groups and correlated with cognitive performance.

Results: Patient groups did not differ with regard to tumor grade or localization. RH gliomas showed higher DMN-RSFC than controls, both within the ipsi- and contra-tumoral hemisphere (F=5.70, p=.010; F=15.60, p<.001), and higher contra-tumoral DMN-RSFC than LH gliomas (p=.001). Differences between ipsi- and contra-tumoral DMN-RSFC varied between patient groups (F=5.54, p=.027), with higher contra- than ipsi-tumoral RSFC in RH gliomas and the opposite pattern being found in LH gliomas. With regard to the FPN, contra-tumoral RSFC was higher in both patient groups as compared to controls (F=14.01, p<.001). Overall, higher contra-tumoral DMN- and FPN-RSFC was associated with worse cognitive performance.

Conclusion: Hemispheric RSFC in glioma patients varied depending on tumor hemisphere and investigated network. While FPN-RSFC was increased in the contralesional hemisphere, DMN-RSFC was increased in the dominant left hemisphere, irrespective of tumor side, but with most prominent alterations being found for DMN-RSFC in RH gliomas. Increases in RSFC may vary in need and efficiency depending on the affected hemisphere. Larger samples are needed to better understand the effect of different tumor characteristics on network dynamics.