Img-17. Changes in Gray Matter Volumes and Their Relation With Neuropsychological Domain Scores in Survivors of a Childhood Posterior Fossa Tumor

Abstract Posterior fossa tumors (PFT) often need neurotoxic radiotherapy (RT). These may affect the brain and contribute to neurocognitive impairment later in life. Therefore, we investigated region-based gray matter volumes (GMV) and their relation to neurocognitive functioning (NF) in PFT survivors. T1-weighted MRI (MPRAGE, resolution=.98x.98x1.2mm) and NF composite scores based on a compressive neuropsychological test battery: total Intelligence, verbal comprehension, working memory, perceptual reasoning, processing speed, language, learning and memory, complex attention (CA), and cognitive flexibility (CF), were analyzed for 17 survivors of PFT (12males, 5females, mean age at diagnosis=8.5±4.5y) and 19 age- and sex-matched controls. Cortical- and subcortical GMV were analyzed with region-based morphometry (RBM, fastsurfer). GMV and NF-scores were compared between controls and survivors, and surgery-only versus RT. Post-hoc analyses correlated GMV with NF-scores and clinical parameters (radiotherapy-dose, time since treatment, and time since diagnosis). Comparing controls with survivors, lower GMV were found for overall subcortical GMV (pFDR=0.020) as well as for several subcortical subregions: bilateral thalamus and bilateral ventral diencephalon (pFDR0.01). Larger GMV was observed in the left inferiotemporal region (pFDR=0.027). Survivors obtained lower NF-scores on all domains (pFDR0.007) except for CA and CF. RT-survivors had lower GMV in bilateral thalamus (pFDR0.05), right ventral diencephalon (pFDR=0.033), and central corpus callosum (pFDR=0.033) compared to surgery-only. Higher GMV were found in bilateral middle temporal regions (pFDR0.05). NF-scores were lower in RT- survivors, but none reached statistical significance after multiple comparison correction. Significant, positive correlations between GMV of bilateral thalamus and right ventral diencephalon was found for the working memory. Differences in GMV and NF scores were observed in PFT survivors. In this limited group, RT-survivors showed more deviant GMV compared to surgery-only survivors and controls. These results also suggest a potential relationship between deviant GMV and worse NF. Notwithstanding, research in larger populations is needed to validate our findings.