Neurocognitive deficits in medulloblastoma survivors and white matter loss

Although previous studies have documented a significant risk of intellectua l loss after treatment for childhood medulloblastoma (MED), the pathophysio logy underlying this process is poorly understood. The purpose of this stud y was to test the hypotheses that (1) patients treated for MED in childhood have reduced volumes of normal white matter (NWM) related to their treatme nt with craniospinal irradiation with or without chemotherapy, and (2) defi cits in NWM among patients surviving MED can at least partially explain def icits in their intellectual performance. Eighteen pediatric patients previo usly treated for MED were matched on the basis of age at the time of evalua tion to 18 patients previously treated for low-grade posterior fossa tumors with surgery alone (mean difference, 3.7 months). Evaluations were conduct ed with age-appropriate neurocognitive testing and quantitative magnetic re sonance imaging by using a novel automated segmentation and classification algorithm constructed from a hybrid neural network. Patients treated for ME D had significantly less NWM (p < 0.01) and significantly lower pull-scale IQ values than those treated for low-grade tumors (mean, 82.1 vs 92.9). In addition, NWM had a positive and statistically significant association with Full-Scale IQ among the patients treated for MED. We conclude that irradia tion- or chemotherapy-induced destruction of NWM can at least partially exp lain intellectual and academic achievement deficits among MED survivors.