On unenhanced CT brain, a glioblastoma multiforme (GBM) classically appears as:
- A Homogeneously hyperdense lesion with no surrounding oedema
- B Well-defined hypodense lesion with peripheral calcification
- C Hypodense lesion with irregular hyperdense rim, central necrosis, and significant surrounding oedema ✓
- D Multiple small hyperdense foci at the grey-white junction
Correct answer: C. Hypodense lesion with irregular hyperdense rim, central necrosis, and significant surrounding oedema
Explanation
GBM on unenhanced CT appears as an irregularly shaped hypodense lesion (representing oedema and necrosis) with irregular hyperdense rim (tumour cells ± haemorrhage), central necrosis, and marked surrounding vasogenic oedema causing mass effect. Post-contrast CT and MRI show irregular ring enhancement. Homogeneous hyperdensity without oedema suggests a lymphoma. Peripheral calcification is seen in oligodendroglioma. Multiple grey-white junction lesions suggest metastases.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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