Medulloblastoma is a form of brain cancer that generally originates between the brain stem and the cerebellum. When it grows, it can block the flow of cerebro-spinal fluid and can mestasisize throughout the central nervous system. It generally affects people under the age of 20 and 40% of patients are diagnosed before the age of five.
Treatment is surgery to remove most of the tumor, followed by radiation therapy or chemotherapy. Survival rate over five years is about 80%, but this number goes down if the tumor has spread, cannot be completely removed, or the patient is under the age of three at the time of diagnosis.