Lithium Treatment to Prevent Cognitive Impairment After Brain Radiotherapy

Late-appearing cognitive side effects after brain radiotherapy is a potential disabling condition in pediatric brain tumor survivors. It can have profound negative effects on education, career options and quality of life. There is no current interventional drug treatment to prevent this intellectual impairment after brain tumor treatment. Primary objective: To assess the efficacy of lithium treatment (up to 7 years) after brain radiotherapy (both whole brain and focal) for central nervous system malignancy in preventing late-appearing cognitive processing speed impairment in children aged 5 or older. Secondary objectives: * To assess the efficacy of lithium treatment through evaluation of other neuropsychological/quality of life test scores. * To assess the efficacy of lithium treatment through evaluation of radiological findings after lithium treatment using Magnetic Resonance Imaging (MRI) of the brain. Exploratory objectives: To explore the feasibility, safety and tolerability of lithium treatment in this patient group, using side effect forms/adverse events (AE) reporting and laboratory measures.