Free-Floating Thrombus in the Carotid Artery: Causes, Characteristics, and Imaging Findings

Atherosclerosis is the most common cause of free-floating thrombus in the carotid artery, with fibrous cap rupture being the main culprit in stroke-related thrombosis, as reported in literature. When a plaque ruptures, it exposes the necrotic core of the lipid to circulation, which leads to thrombosis and stroke events. Free-floating thrombus is characterized as a cylindrical thrombus attached to the arterial wall, surrounded by blood flow at the distal end, and exhibiting periodic movements related to the cardiac cycle. On CTA, it appears as a filling defect in the carotid artery lumen surrounded by contrast agent, described as the 'donut sign,' and extending to some extent in the direction of the head. The ultrasonography features of this case match the above imaging findings accurately.