Evidence of supratentorial white matter injury prior to treatment in children with posterior fossa tumors using diffusion MRI.

Background: Pediatric brain tumor survivors can have neurocognitive deficits that negatively impact their quality of life, but it is unclear if deficits are primarily caused by treatments, such as radiotherapy, or manifest earlier due to the tumor and related complications. The aim of this work is to characterize white matter injury caused by brain tumors, unrelated to treatment effects, and explore heterogeneity in these white matter abnormalities between individual patients. Methods: We used diffusion tensor imaging and neurite orientation dispersion diffusion imaging to assess white matter injury in 8 posterior fossa tumor patients. A novel one-against-many approach was used by comparing an individual patient to 20 age- and sex-matched healthy controls to assess variability in white matter abnormalities between the posterior fossa tumor patients. White matter was analyzed at presentation (prior to treatment), postsurgery (24-72 hours after surgery), and at follow-up (3-18 months after surgery). Results: We demonstrate white matter abnormalities in 5 posterior fossa tumor patients before treatment, likely related to tumor-induced hydrocephalus, which persisted after treatment. White matter changes were complex and patient-specific, and group-based comparisons with control subjects may fail to detect these individual abnormalities. Conclusions: Identifying pretreatment white matter injury in posterior fossa tumor patients highlights the importance of personalized assessment of brain microstructure, which should be considered in minimizing neurocognitive deficits to improve patient quality of life.