gms | German Medical Science

Objective: Functional integrity is believed to be tightly bound to structural integrity in the healthy brain. Diffuse infiltrative glioma however disrupts structural white matter integrity and may impact on functional connectivity, both of peritumoral and distant brain regions. Whether structural and functional connectivity (SC, FC) are interdependent in glioma patients, diverge regionally, or differ depending on tumor growth dynamics remains unclear. We analyzed potential correlations of FC and SC in glioma patients under consideration of tumor site and IDH mutation status.

Methods: 27 glioma patients (15 IDH_mut, 12 IDH_wt) and 27 healthy controls underwent diffusion-weighted imaging and resting-state-fMRI. Patients were enrolled preoperatively. Whole-brain (WB) and default-mode network (DMN) parcellations were based on the Brainnetome atlas, and corresponding SC and FC matrices were determined for each subject. SC measures comprised the number of fibers (NF), and the mean fractional anisotropy (FA) of fibers connecting two regions, based on free-water corrected probabilistic tractography. FC measures comprised the correlation between the mean time-series of structurally connected regions. SC as well as FC submatrices of ipsi-, contra-lesional and interhemispheric connectivity were compared across groups, and partial correlations (p<0.05, uncorrected) analyzed for corresponding SC and FC submatrices.

Results: Patient groups and healthy controls differed neither in FC nor in NF. By trend, however, mean FA values were lower in IDH_wt as compared to IDH_mut patients across all submatrices. Correlation analyses revealed intramodal associations within SC and FC matrices, both for patients and controls. But while in controls, FA and NF were associated across all submatrices, only few associations were found in IDH_mut patients (FA_contra and FA_inter with NF_ipsi and NF_contra), but none in the IDH_wt group. Furthermore, healthy subjects showed SC-FC correlations for WB as well as within the DMN, while neither IDH_mut nor IDH_wt patients showed any association between SC and FC measures.

Conclusion: Microstructural integrity of the structural connectome seemed to be altered in the prognostically less favorable IDH_wt patients, even in tumor distant regions. While FC may not yet be altered, the dissociation of SC and FC might be an early indicator of network desintegration in glioma patients.