QOL-29. SUPRA- AND INFRATENTORIAL TRACTOGRAM CHANGES IN CHILDHOOD POSTERIOR FOSSA TUMOR SURVIVORS

Abstract

INTRODUCTION: Brain tumor survivors frequently suffer from cognitive deficits. However, microstructural reorganization of white matter following treatment remains unclear. Recently, more tract-specific (fixelbased) analysis was introduced to dissociate micro-from macrostructural changes. METHOD: In this study, diffusion-weighted MR-scans were acquired in 21 childhood posterior fossa tumor tumor survivors and 21 matched controls. Mean age at diagnosis = 8.3 years; age range = [16-34] years; >2 years out of treatment, pilocytic astrocytoma (n=8), ependymoma (n=1) or medulloblastoma (n=12) at the University Hospitals of Leuven. An echo-planar, multi-shell diffusion imaging scheme (b=700,1000,2800s/mm2) was applied. P(re-)rocessing was performed using MRtrix3 and FSL. Besides typical diffusion-derived parameters (DTI-derived Fractional Anisotropy (FA) and Apparent Diffusion Coefficient (ADC)), we compared advanced parameters: fixel-based Apparent Fiber Density (AFD) and Fiber Cross-section (FC) to dissociate microstructural from macrostructural white matter properties, respectively. Non-parametric testing was performed for group comparisons. Finally, microstructural AFD values were compared between cranial irradiated and non-irradiated patients, and correlated with WAIS intelligence subscales within the patient subgroup. RESULTS: Differences in DTI-derived parameters and microstructural changes (AFD) were found in both supratentorial and infratentorial regions, whereas lower macrostructural changes (FC) were found only in cerebellar tracts. Microstructural AFD values were lowest in irradiated patients (F=11.181, p=.004), and correlated with working memory (r=.461, p=.047) and processing speed (r=.527, p=.020). DISCUSSION: Macrostructural changes were very specific for cerebellar tracts, probably due to neurosurgery and the remaining cavity. Specific lower microstructural values in supratentorial regions rather suggest systemic treatment or cascade effects, which might highly affect attentional functioning.