Medulloblastoma is a rare but devastating childhood brain cancer. This cancer can spread through the spinal fluid and be deposited elsewhere in the brain or spine. Radiation therapy to the whole brain and spine followed by an extra radiation dose to the back of the brain prevents this spread and has been the standard of care. However, the radiation used to treat such tumors takes a toll on the brain, damaging cognitive function, especially in younger patients whose brains are just beginning to develop.