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Medulloblastoma

Last modified by Hussein Abdallah on 2025/05/26 00:30

 

FACTS

#1 most common pediatric brain malignancy

  • WHO grade IV 
  • embryonal tumor 
  • typical location: cerebellum (in vermis near apex of roof of 4th ventricle) + dorsal brainstem 
  • BOARDS: sonic hedgehog gene (SHH) mutations cause medulloblastoma (along with holoprosencephaly). Other frequently associated mutations are in the genes MYCN, CDK6, CTNNB1, and WNT. 

CONSULT

HPI 

usual presenting sx: HA, n/v, ataxia 

infants: irritability, lethargy, macrocrania

Drop mets ROS: back pain, urinary retention, leg weakness 

Associated with Fanconi Anemia

FOCUSED EXAM

truncal and appendicular ataxia

nystagmus

EOM palsies

head size (infants) 

IMG 

MRI Brain w/wo = enhancing midline in children (lateral in adults more likely), T2 = heterogenous (cysts, vessels, Ca2+)  

MR spectrography: high Chol, low NAA  

- ependymomas vs. medulloblastomas

* ependymoma = floor

* medulloblastomas = roof  

A/P

At the time of consult
[ ] MRI pan neuro axis w/wo to evaluate for drop mets 
[ ] Optho c/s for papilledema 
[ ] Neuro-oncology c/s 
 

3 Pronged Approach

[ ] Surgical debulking: better to reave last remnant in the brainstem
[ ] Radiation: exact fractions will vary based on risk stratification (molecular diagnosis)
[ ] Chemotherapy: options include cisplatin, lomustine, vincristine, cyclophosphamide, cyclophosphamide, etoposide, high dose IV MTX/intrathecal MTX Of mafosfamide or intraventricular methotrexate 

[ ] LP post-op for CSF cytology 
[ ] Counsel: this is a life changing diagnosis, careful and appropriate delivery to family is important. 

- post-op cerebellar mutism is a common complication in cerebellar tumors for children (up to 53% in medulloblastomas). Risk factors include midline location, brainstem involvement (Greenberg)
- 30-40% will require permanent VP shunt 
- there is a risk of tumor spread with surgery 
- long-term survivors have high risk of endocrine/cognitive sequalae from treatments
- poor predictors of prognosis: younger age (<3 years), disseminated disease, inability to perform GTR, poor KPS 

Classification

Histologic criteria

1. classic

2. desmoplastic / nodular (Nevoid Basal Cell Carcinoma, Gorlin Syndrome)

3. extensive nodularity

Molecular criteria

WNT-activated

SHH-activated (TP53 WT vs. mutant)

 

Holoprosencephaly, Agenesis of the corpus callosum

Figure 1: Holoprosencephaly and medulloblastoma share a connection: both involve mutations in SHH gene