Fact-sheet: Medulloblastoma
Updated on 04/18/2017 at 7:18 AM
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Definition
Medulloblastoma is the most common primary central nervous system tumor in children.
Peak incidence is between 4 and 5 years of age.
The preferential site is the fourth ventricle.
Medulloblastoma is an aggressive grade IV tumor according to the WHO classification. It is most often midline, arising from the vermis toward the fourth ventricle with early obstruction of CSF outflow pathways.
Medulloblastoma in adults tends to be hemispheric in location.
Leptomeningeal dissemination is common and should be screened for on postcontrast T1-weighted imaging of the brain and spinal cord.
Extra-CNS metastases are common (lymph nodes, lungs, bone).
Clinical features
Rapidly progressive symptoms.
Headaches, vomiting: first manifestations of increased intracranial pressure induced by hydrocephalus.
Then diplopia due to VI nerve palsy and axial cerebellar ataxia.
Seizures.
CT
Triventricular hydrocephalus with signs of transependymal CSF resorption.
Slightly hyperdense lesion, rarely with small nodular calcifications.
MRI
Hypo- or isointense mass on T1, hyperintense on T2 (fleshy component) with necrotic and cystic components.
Small hemorrhagic foci on T2*.
Intense and heterogeneous enhancement.
Moderate peritumoral edema.
In adults, medulloblastoma presents sharper margins than in children.
Management
Treatment by surgical resection combined with craniospinal radiotherapy +/- chemotherapy.
5-year survival 60%.
Brain and spinal MRI surveillance every 6 months for the first 5 years, then annual MRI.
