Img-04. Association Between Microstructural Integrity of Brain Substructures and Neurocognitive Outcomes: A Multi-Trajectory Analysis in Childhood Brain Tumor Survivors

Abstract BACKGROUND The relationship between the brain’s microstructural integrity and neurocognitive outcomes is not well characterized in childhood brain tumor survivors. In healthy children, mean diffusivity (MD) generally decreases and fractional anisotropy (FA) increases with age as the brain progressively myelinates and develops. Increasing MD and decreasing FA is suggestive of microstructural injury. We investigate the association between longitudinal neurocognitive outcomes and change in MD and FA in childhood brain tumor survivors. METHODS Patients diagnosed with a brain tumor at 20 years of age with ≥ 2 neurocognitive assessments and paired DTI at each neurocognitive timepoint were retrospectively identified and eligible for inclusion. Multi-trajectory modeling was applied to cluster patients into distinct neurocognitive trajectories based on intelligent quotient, processing speed and working memory. Linear mixed models were used to determine whether the clusters were associated with change in MD and FA over time. RESULTS A total of 61 patients were eligible with 151 neurocognitive assessments paired with DTI. Mean follow-up was 4.8 years. Multi-trajectory modeling identified two clusters of patients with distinct neurocognitive trajectories. Compared to the low-performance group, the high-performance group (45.5%) had higher baseline neurocognitive scores with less decline in all neurocognitive outcomes. The high-performance group was also associated with a greater decrease in MD and greater increase in FA of the hippocampus and several white matter tracts such as the corpus callosum, pontine crossing tract, anterior limb of the internal capsule and inferior cerebellar peduncle, after adjusting for age and sex (all p0.05). Additionally, the high-performance group was associated with a greater increase in FA in the superior, middle and inferior frontal gyri (all p0.05). CONCLUSIONS The high-performance neurocognitive group was associated with greater microstructural integrity over time in multiple brain substructures compared to the low-performance group, as measured by change in fractional anisotropy and mean diffusivity.