A 68-year-old man with atrial fibrillation presents with sudden right-sided hemiplegia, global aphasia, and forced gaze deviation to the left. NIHSS is 18. Non-contrast CT head performed 90 minutes after symptom onset shows the finding marked as **A** in the diagram — a hyperdense appearance of the left MCA M1 segment measuring 50–60 Hounsfield units. CT angiography confirms left M1 occlusion. Which of the following best describes the pathophysiological significance of the structure marked **A**?
A. Indicates chronic atherosclerotic calcification and requires conservative management with antiplatelet therapy alone
B. Represents acute thrombus within the vessel lumen and has high specificity (>90%) for large vessel occlusion, warranting urgent thrombolysis and mechanical thrombectomy
C. Reflects elevated hematocrit or polycythemia and typically resolves spontaneously without intervention
D. Suggests acute hemorrhagic transformation and is a contraindication to thrombolytic therapy
Explanation
Why option 1 is right
The hyperdense MCA sign (dense artery sign) represents acute thrombus within the vessel lumen and has high specificity (>90%) for large vessel occlusion. In this patient with acute stroke presentation (right hemiplegia, global aphasia, forced gaze deviation to left, NIHSS 18) and confirmed M1 occlusion on CTA within 90 minutes of symptom onset, the hyperdense MCA segment is the radiological hallmark of acute thrombotic occlusion. This finding, combined with early ischemic changes (loss of insular ribbon, ASPECTS score 7), mandates immediate IV thrombolysis (alteplase 0.9 mg/kg or tenecteplase) with door-to-needle target <60 minutes, followed by urgent mechanical thrombectomy, as per AHA/ASA 2019 guidelines for LVO within the 4.5-hour window.
Why each distractor is wrong
Option 2: Chronic atherosclerotic calcification typically appears as bilateral hyperdense foci and has low specificity; it does not present with acute neurological deficits and does not require emergent intervention. The acute clinical presentation and CTA confirmation of occlusion exclude chronic atheroma.
Option 3: The hyperdense MCA sign represents thrombus, not hemorrhage. Acute hemorrhagic transformation is a complication that may occur after thrombolysis, not a finding that contraindicates it. Non-contrast CT here shows no blood; the hyperdensity is the thrombus itself.
Option 4: While elevated hematocrit or polycythemia can cause vessel hyperdensity, this is typically bilateral and asymptomatic. The unilateral hyperdense MCA in the setting of acute stroke symptoms, focal neurological deficits, and CTA-confirmed occlusion is pathognomonic for acute thrombus, not hematocrit elevation.
High-YieldNEET PG
The dense artery sign (hyperdense vessel on NCCT) has >90% specificity for acute thrombus and is a key radiological trigger for emergent thrombolysis and thrombectomy in acute ischemic stroke within appropriate time windows.
