Medulloblastoma is a fast-growing brain tumor that starts in the lower back part of the brain (cerebellum) and can spread to other parts of the brain and spine. It is the most common malignant brain tumor in children, but it can also occur in adults. Because it grows quickly and blocks the flow of cerebrospinal fluid, symptoms usually get worse quickly over days to weeks. The first symptom is usually a headache that is worse in the morning and gets better after the person vomits or sits up. The headache is caused by the tumor blocking the flow of cerebrospinal... Learn more