Longitudinal cortical thickness changes in children with posterior fossa tumors

Abstract: Background Children with posterior fossa tumors (PFTs) are at risk of long-term neurocognitive deficits, yet the impact of tumor grade and treatment intensity on cortical development remains poorly understood. The aim of this study was to determine whether cortical thickness trajectories differ between children with low- versus high-grade PFTs and whether radiation dose influences cortical development in medulloblastoma patients. Methods: We conducted a retrospective longitudinal study of 55 children (37 low-grade, 18 high-grade medulloblastoma) diagnosed between 2018 and 2020. A total of 406 T1-weighted MRI scans acquired up to five years post-diagnosis were processed using CAT12 in SPM12 to estimate cortical thickness. Vertex-wise linear mixed-effects models assessed cortical thickness changes over time, adjusting for age at diagnosis, sex, and hydrocephalus. Within the high-grade group, we evaluated the effect of craniospinal irradiation (CSI) dose (23.4 vs. ≥36 Gy) on cortical development. Results: Children with low-grade tumors showed significant bilateral cortical thinning over time, consistent with typical neurodevelopment. In contrast, medulloblastoma patients treated with surgery, chemotherapy, and radiation therapy showed relative cortical stability across follow-up. Significant group-by-time interactions were observed, with low-grade patients demonstrating greater cortical thinning in parietal, temporal, and occipital regions. No significant differences in cortical trajectories were found between high- and standard-dose CSI subgroups. Conclusions: Cortical development trajectories in pediatric PFT survivors differ by tumor grade and treatment intensity. While low-grade patients exhibit expected maturational thinning, cortical stability in high-grade patients may reflect disrupted neurodevelopment. These findings underscore the need for longitudinal neuroimaging in pediatric neuro-oncology survivorship care.