On axial CT brain, the 'dense MCA sign' (hyperdense middle cerebral artery) is seen. This sign indicates:
- A Arteriovenous malformation of the MCA territory
- B Calcification of the MCA wall in an elderly patient
- C Acute thrombus within the MCA lumen ✓
- D Contrast enhancement of the MCA after IV contrast
Correct answer: C. Acute thrombus within the MCA lumen
Explanation
The hyperdense MCA sign on non-contrast CT represents acute intraluminal thrombus within the MCA (Hounsfield units >70, compared to ~40 for normal brain). It is an early sign of acute ischaemic stroke, visible within 6 hours of occlusion, and indicates a large territory at risk. MCA calcification is typically linear and bilateral in the wall, not filling the lumen. AVMs show serpiginous vessels. Contrast is not used in hyperacute stroke CT.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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