Makindo Medical Notes

Related Subjects: |Brain tumour s |Astrocytomas |Brain Metastases |Tuberous sclerosis |Turcot's syndrome |Lhermitte Duclos Disease |Oligodendroglioma |Acute Hydrocephalus |Intracranial Hypertension |Primary CNS Lymphoma (PCNSL) |Meningioma

🧠 Medulloblastoma is a highly malignant brain tumour, most common in children but can also occur in adults. 🎯 Origin: the cerebellum or posterior fossa, affecting balance, coordination, and motor control. ⚠️ Symptomatic cases often present with hydrocephalus due to CSF obstruction.

📌 About Medulloblastoma

• 👶 The commonest malignant brain tumour in children.
• Part of the primitive neuroectodermal tumour (PNET) family.
• Posterior fossa location is typical in paediatrics.
• Spreads via CSF pathways (drop metastases in spinal cord) 🌊; systemic spread to bone is rare.

🧬 Aetiology

• Malignant primitive neuroectodermal tumour.
• Arises most often in the midline cerebellar vermis (especially in children).
• Genetic pathways involved include WNT, SHH, and MYC amplification in aggressive forms.

🔬 Histological Subtypes

• Classic: Sheets of small, round, blue cells with hyperchromatic nuclei.
• Desmoplastic/Nodular: Reticulin-free nodules; better prognosis 👍.
• Large Cell/Anaplastic: Aggressive, pleomorphic cells; poor prognosis ⚠️.
• Extensive Nodularity: Often in infants; nodules with reticulin fibres.

🧪 Molecular Subgroups

• WNT-activated: Best prognosis (~90% 5-year survival); midline tumours.
• SHH-activated: Intermediate prognosis; often in cerebellar hemispheres.
• Group 3: Worst prognosis; MYC amplification, frequent metastasis.
• Group 4: Most common; intermediate prognosis, often with i(17q) abnormality.

🩺 Clinical Features

• 🎯 Raised ICP: Headache, nausea, vomiting due to obstructive hydrocephalus.
• ⚖️ Cerebellar signs: Truncal ataxia, gait disturbance, nystagmus.
• 🌀 Brainstem involvement: Cranial nerve palsies, diplopia.
• 🌊 CSF spread: Back pain, limb weakness from spinal drop metastases.

📷 Investigations

• MRI Brain (gold standard):
  • T1: Hypo/isointense; heterogeneous contrast enhancement.
  • T2: Hyperintense mass; surrounding oedema clear.
  • FLAIR: Highlights peritumoural oedema & non-enhancing tumour areas.
• CT Brain: Used in emergencies; shows hyperdense posterior fossa lesion, hydrocephalus, and possible calcification.
• Spinal MRI: Whole spine at diagnosis & follow-up → detect drop metastases.
• PET/CT: Occasionally used for metabolic activity or metastasis detection.

💊 Management

• Surgery: Maximal safe resection to debulk tumour and relieve pressure.
• Radiotherapy: Craniospinal irradiation (CSI) with boost to tumour bed 🎯.
• Chemotherapy: Especially in high-risk or younger patients to reduce radiotherapy dose toxicity.
• Rehabilitation: Physiotherapy, neurocognitive support, and long-term endocrine monitoring.

📉 Prognosis

• Depends on molecular subgroup, age, resection extent, and presence of metastases.
• WNT subtype → best outcome ✅.
• Group 3 with MYC amplification → worst prognosis ⚠️.

📚 References

• Louis DN, et al. WHO Classification of CNS Tumours. IARC, 2021.
• NICE. (2021). Brain tumours (primary) and brain metastases in adults.
• Pizer BL, Clifford SC. Medulloblastoma: biology, genetics and treatment. Br J Cancer. 2009.