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 fluid, which increases pressure inside the brain.

Nausea and vomiting are also common. The vomiting is often sudden and forceful, and it may happen without any nausea beforehand. It is usually worse in the morning and may get better as the day goes on.

Balance and coordination problems are another early sign. The person may have trouble walking, standing on one foot, or writing. They may also have trouble with fine motor skills, such as buttoning a shirt or tying shoelaces.

Eye problems are also common. The person may have double vision, blurred vision, or trouble moving their eyes. They may also have a blank stare or rapid eye movements.

Behavioral changes are also possible. The person may become irritable, tired, or withdrawn. They may also have trouble concentrating or remembering things.

Seizures are also possible, but they are not as common as the other symptoms.