MRI shows a mass at the cerebellar vermis in a 7-year-old child, which is isointense on T1, hyperintense on T2, shows restricted diffusion, homogeneous enhancement, and 'drop metastases' along the spinal cord. The MOST likely diagnosis is:
- A Medulloblastoma (PNET) ✓
- B Juvenile pilocytic astrocytoma
- C Ependymoma
- D Brainstem glioma
Explanation
Medulloblastoma is the most common malignant paediatric brain tumour, arising from the cerebellar vermis in young children. Key MRI features include midline cerebellar location, restricted diffusion (highly cellular tumour), homogeneous enhancement, and a propensity for CSF dissemination (drop metastases coating the spinal cord/cauda equina). Juvenile pilocytic astrocytoma is typically hemispheric, cystic with a mural nodule, and no restricted diffusion. Ependymoma arises from the floor of the 4th ventricle and may extrude through the foramina ('plastic ependymoma'). Brainstem glioma is intrinsic to the pons.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.