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Medulloblastoma Brain Tumor Highyield Notes for USMLE, NEET PG, FMGE and Board Exams

Medulloblastomas are the most common malignant brain tumor of childhood

It is accounting for ~20% of all primary CNS tumors among children. 

They arise from granule cell progenitors or from multipotent progenitors from the ventricular zone

Approximately 5% of children with medulloblastoma have an inherited syndrome, such as:

  • Gorlin
  • Turcot
  • Li-Fraumeni

Histology of Medulloblastoma Brain Tumor:

Highly cellular tumors with abundant dark staining, round nuclei, and rosette formation (Homer-Wright rosettes). 

Medulloblastoma classification:

In the 2016 WHO pathologic classification, they have been divided into four molecular subgroups:

1. WNT-activated (primarily affects children and has the best outcome); 

2. SHH-activated (affects adults, infants, and children with the younger patients having the better outcome and adults doing poorly); 

3. non-WNT/non-SHH, group 3 (frequently has disseminated CNS disease at diagnosis and has the worst outcome); and 

4. non-WNT/non-SHH, group 4 (30% have metastases at diagnosis, but 5-year progression-free survival is 95%). 

Common presentation of Medulloblastoma:

Headache, dizziness, visual disturbances

Truncal ataxia, seizures, sensory deficit

Nausea, vomiting

Medulloblastoma Brain Tumor
Medulloblastoma Brain Tumor

Diagnosis of Medulloblastoma:

MRI is the imaging modality of choice (ref)

Enhancing 4th ventricular mass

Hommer Wright rosettes

Sometimes associated with hydrocephalus

Treatment of Medulloblastoma:

Maximal surgical resection, craniospinal irradiation, and chemotherapy with agents such as cisplatin, lomustine, cyclophosphamide, and vincristine. 

Prognosis for Medulloblastoma:

65-85% Survival dependent on stage/type

Poorer prognosis in infants

Reference: Harrison’s Principles of Internal Medicine, 20th Edition

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