Introduction: Posterior fossa syndrome (PFS) occurs post-operatively in approximately 10% of patients who undergo resection of a posterior fossa tumor. Although PFS is classically considered to be a self-limited disease, survivors of PFS have been found to experience long-term cognitive disability. White matter injury (WMI) can affect structural connectivity and is often associated with disabilities. Functional connectivity reflects the temporal interactions of separated brain regions.
Methods: Institutional Review Board approval was obtained to enroll pediatric brain tumor survivors for cognitive testing and magnetic resonance imaging (MRI) data collection. Among the imaging data used, 48 patients were in the control group who underwent posterior fossa tumor resection without PFS and 13 patients were in the group that had tumor resection with PFS. Analysis of the DTI data was performed with tract-based spatial statistics (TBSS) and DSI studio. Functional connectivity was assessed with correlation maps using time series extracted from seed regions of interest.
Results: Among patients with PFS, there were significant long-term decrease of fractional anisotropy in numerous white matter tracts, including corpus callosum body and genu, cingulum inferior and superior, corona radiata, superior longitudinal fasciculus, and fornix stria terminalis. These changes in tractography were observed with both TBSS and DSI studio analysis. Among these patients with PFS, there was also significantly decreased functional connectivity in multiple resting state networks, including limbic, dorsal attention, ventral attention, and default mode network.
Conclusion : Patients who experienced post-operative PFS had significantly decreased FA in multiple white matter tracts indicating long-term WM microstructure injury compared to patients who underwent resection of a posterior fossa tumor and never experienced PFS. These patients also demonstrated long-term decreased functional connectivity in numerous resting state networks. DTI and functional connectivity analysis has the potential to be used as a biomarker for assessing long-term cognitive injury in patients who experienced PFS.
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