How does a medulloblastoma affect the body?

A medulloblastoma can affect the brain by putting pressure on it. This pressure on the brain is what causes frequent vomiting, usually the first sign of a medulloblastoma. The pressure occurs when the tumor disrupts flow of certain cerebrospinal fluid pathways. In some children, hydrocephalus, or "water on the brain," may occur. Hydrocephalus is the result of an abnormally high level of cerebrospinal fluid in the ventricles. This can cause the skull to expand in young children and babies in whom skull bones have not been firmly set.