Medulloblastomas are invasive and rapidly growing childhood CNS tumors that develop in the posterior fossa (containing the brain stem and cerebellum). Diagnosis is based on MRI and biopsy/tumor resection. Treatment is a combination of surgery, radiation therapy, and chemotherapy.
Medulloblastoma is the most common malignant posterior fossa tumor in children and represents about 20% of all pediatric CNS cancers. It has a bimodal peak at age 3 to 4 yr and at age 8 to 10 yr but can occur throughout childhood. Medulloblastoma is a type of primitive neuroectodermal tumor (PNET).
Etiology of medulloblastoma is unknown in most patients, but medulloblastoma may occur with certain syndromes (eg, Gorlin syndrome, Turcot syndrome).
MRI with gadolinium contrast is the test of choice for initial evaluation of possible medulloblastoma. Definitive diagnosis is made using tumor tissue obtained by biopsy or ideally by gross total resection of the tumor at initial presentation.
Once the initial diagnosis is established, staging and risk group determination are critical in medulloblastoma.
Staging tests include
Risk assessment is based on amount of residual tumor, and evidence of spread of disease:
Prognosis depends on the stage, histology, and biologic (eg, histologic, cytogenetic, molecular) parameters of the tumor and patient age, but generally
Age > 3 yr: Likelihood of 5-yr disease-free survival is 50 to 60% if the tumor is high risk and 80% if the tumor is average risk.
Age ≤ 3 yr: Prognosis is more problematic, in part because up to 40% of children have disseminated disease at diagnosis. Children who survive are at risk of severe long-term neurocognitive deficits (eg, in memory, verbal learning, and executive function).