Medulloblastoma

Medulloblastoma is a fast-growing brain tumor that starts in the cerebellum, at the back of the brain, which controls balance and coordination. It is the most common malignant brain tumor in children, usually diagnosed between ages 3 and 8.

Causes and risk factors

Most cases have no known cause. A few are linked to inherited conditions such as Gorlin syndrome, Turcot syndrome or Li-Fraumeni syndrome.

Symptoms

• Morning headaches and vomiting caused by raised pressure in the brain
• Unsteady walking, clumsiness and problems with balance
• Double vision or abnormal eye movements
• Tiredness and changes in behaviour
• In babies, a growing head size and a bulging soft spot

Classification

Types (by appearance)

Classic, desmoplastic/nodular, extensive nodularity and large cell/anaplastic medulloblastoma.

Molecular subgroups

• WNT-activated — the most favourable outlook
• SHH-activated — TP53 wild-type or mutant
• Group 3 and Group 4

The subgroup, age and spread of the tumor together define the risk and the intensity of treatment.

Diagnosis needs brain and spine imaging, surgery to obtain tissue, and tests of the spinal fluid.

Physical exam and medical history

Including a full neurological examination.

Neurological exam

Tests balance, coordination, reflexes, vision and eye movements.

Magnetic resonance imaging (MRI)

MRI of the brain and the whole spine, with contrast, shows the tumor and any spread along the spinal cord.

Computed tomography (CT) scan

Often the first emergency scan when a child has headache and vomiting.

Lumbar puncture (spinal tap)

Usually done about two weeks after surgery to look for tumor cells in the spinal fluid.

Biopsy and tumor analysis

The tissue removed at surgery is examined under the microscope and with molecular tests to define the subgroup.

Treatment combines surgery, radiation and chemotherapy, carefully adjusted to the child's age and risk group.

Surgery

The neurosurgeon removes as much of the tumor as is safely possible. Pressure in the brain may need to be relieved with a drain or shunt.

Radiotherapy

Craniospinal radiation (brain and spine) with an extra dose to the tumor site, for children over about 3 years of age. Dose is reduced for average-risk disease to protect the developing brain.

Chemotherapy

Given after radiation (or instead of radiation in very young children) to destroy remaining tumor cells.

Bone marrow transplant

High-dose chemotherapy with autologous stem cell rescue is used for infants and for some high-risk or relapsed tumors.

Targeted therapy

SHH-pathway inhibitors and other targeted agents are being studied for selected tumors.

Follow-up care

Regular MRI scans and support for learning, hearing, hormones, growth and emotional wellbeing.

Our pediatric neuro-oncology team works with neurosurgeons and radiation oncologists.