A 62-year-old man presents with sudden right arm weakness and aphasia. Non-contrast CT head done 90 minutes after onset shows a linear hyperdense structure in the left Sylvian fissure extending from the region of the circle of Willis. This finding indicates:
- A Acute thrombus in the left M1 segment of the middle cerebral artery ✓
- B Calcification of the left middle cerebral artery wall
- C Subarachnoid haemorrhage confined to the left Sylvian fissure
- D Contrast extravasation from an aneurysm
Correct answer: A. Acute thrombus in the left M1 segment of the middle cerebral artery
Explanation
The hyperdense middle cerebral artery sign represents fresh thrombus within the vessel, with attenuation around 60 to 80 HU, and predicts a large territory infarct with poor outcome if untreated. Calcified atherosclerotic vessels are much denser, above 120 HU, thinner, and usually bilateral, which kills that distractor. Subarachnoid blood fills cisterns rather than tracing a single arterial segment.
Reference: Osborn's Brain, 2nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.