Medulloblastoma

Patients present most commonly with symptoms associated with increased intracranial pressure and cerebellar dysfunction, which may include vomiting, headache, nausea, visual changes (eg, double vision), and unsteady walking or clumsiness.

• 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 cerebrospinal fluid cytology

• Postoperative brain 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.

Molecular grouping is also part of the diagnostic evaluation, and treatments are evolving based on these groups. The major molecular groups for medulloblastoma are WNT-activated, SHH-activated, group 3, and group 4. New subgroups have emerged at a more granular level below the four major molecular groups.

(See also the World Health Organization's 2021 classification of tumors of the central nervous system.)

• Surgery, radiation, and chemotherapy

Treatment of medulloblastoma includes surgery, radiation, and chemotherapy.

Cure with chemotherapy alone with regimens that avoid or delay radiation has occurred in some children < 3 years of age, usually in combination with surgery plus high-dose chemotherapy with autologous hematopoietic stem cell transplantation.

Combination therapy typically provides the best long-term survival.

Prognosis depends on age, stage, histology, cytogenetics, and molecular parameters of the tumor (1):

• Age > 3 years: Likelihood of 5-year disease-free survival is 60 to 70% if the tumor is high risk, and 80% if the tumor is average risk.

• Age ≤ 3 years: Prognosis is more problematic, in part because up to 40% of children have disseminated disease at diagnosis and radiation therapy is typically avoided/delayed in this age group. Children who survive are at risk of severe long-term neurocognitive deficits (eg, in memory, verbal learning, and executive function).

Molecular group WNT-activated has the best prognosis with 90 to 100% overall survival. Ongoing pediatric clinical trials are being done to determine whether therapy can be reduced in patients with WNT-activated medulloblastoma.

The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

1. World Health Organization (WHO): The 2021 WHO Classification of Tumors of the Central Nervous System: A summary