Pearls & Oy-sters: Giant descending aortic arch donut sign: Retrograde embolism as a cause of acute ischemic stroke.

A 65-year-old woman presented with sudden-onset global aphasia and right-sided hemiplegia (NIH Stroke Scale score 22). She arrived to the hospital 1 hour and 55 minutes after symptoms onset. Her medical history was relevant for hypertension, idiopathic deep vein thrombosis (treated with apixaban for 3 months, 1 year earlier), smoking, and obesity. She was not on antiplatelet or anticoagulant therapy. Initial CT of the head showed early ischemic changes in the left insular ribbon and caudate head. A CT angiogram of the head showed an occluded left middle cerebral artery (MCA) with potentially reversible ischemia on CT perfusion imaging. A CT angiogram of the neck evidenced a 6.8 cm linear hypodensity extending distally from the proximal descending aorta, 39 mm away from the origin of the left common carotid artery (figure, A). On axial imaging, the appearance was that of the donut sign.