Medulloblastomas usually develop in a part of the brain called the posterior fossa, and may sometimes spread to other parts of the brain or spinal cord, through the cerebrospinal fluid (CSF) that surrounds the brain. They are most commonly found in the cerebellum, an area of the posterior fossa that controls coordination and balance. The signs and symptoms of a medulloblastoma are usually caused by increased pressure in the brain. Symptoms may include:

abrupt onset of headaches, especially in the morning
nausea and/or vomiting
feeling extremely tired
loss of balance and co-ordination which may lead to difficulty walking
abnormal eye movements
blurry vision caused by swelling of the optic disc at the back of the eye (papilloedema)