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Medulloblastoma

By John J. Gregory, Jr., MD, Goryeb Children's Hospital, Atlantic Health;UMDNJ New Jersey Medical School

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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).

Symptoms and Signs

Patients present most commonly with vomiting, headache, nausea, visual changes (eg, double vision), and unsteady walking or clumsiness.

Diagnosis

  • MRI

  • Histologic evaluation of biopsy specimen or entire resected tumor

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

  • MRI of the entire spine

  • Lumbar puncture for CSF cytology

  • Postoperative MRI to assess for any residual tumor

Risk assessment is based on amount of residual tumor, and evidence of spread of disease:

  • High risk: Postoperative residual disease is > 1.5 cm2 or there is disseminated microscopic or gross disease.

  • Average risk: Postoperative residual disease is < 1.5 cm2 and there is no dissemination.

Prognosis

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).

Treatment

  • Surgery, radiation, and chemotherapy

Treatment of medulloblastoma includes surgery, radiation, and chemotherapy. Cure with chemotherapy alone has been shown in some children < 3 yr of age. Combination therapy typically provides the best long-term survival.

* This is the Professional Version. *