Mobile lesions of the carotid artery, which can generally be found by ultrasonography (US), are treated as unstable plaque. Mobile lesions ≥2 mm in diameter were observed for 7 patients (6 men, 1 woman) treated in our hospital between January 2002 and July 2015. Mean age was 67.8 years (range, 52-84 years). Diagnosis was major stroke in 1 patient and transient ischemic attack/minor stroke in 6 patients. Surgical treatment was performed in 6 cases: carotid endarterectomy in 4 and carotid artery stenting in 2. The remaining patient did not undergo surgery because of a marked reduction in size of the mobile lesion after observation for 5 days. Surgical intervention was performed at a mean of 20 days (range, 1-52 days) after onset. None of the 6 operated patients had any complications pre- or postoperatively. We proposed four mechanisms for mobile lesions on imaging, based on pathological findings and responses to antithrombotic therapy: floating plaque entangled with ulcer edge; mobile thrombus adherent to ulcer edge or erosion of the plaque; pulsatile dissected arterial wall; and oscillating lodged embolus in the carotid artery. Choosing the operative procedure and timing in accordance with the underlying mechanism is important.
