Lodged Thrombus: A Pitfall for Diagnosing Carotid Web Using Contrast-Angiography.

Carotid web, a form of fibromuscular dysplasia, involves a thin, membrane-like tissue in the carotid bulb that can cause thrombus formation and is linked to cryptogenic ischemic stroke. Diagnosis typically relies on detecting a shelf-like filling defect in digital subtraction angiography or 3D-CT angiography. We report a case of the symptomatic carotid web that could not be diagnosed using DSA or 3D-CT angiography due to a lodged thrombus but was successfully identified through carotid ultrasonography. A 44-year-old woman with a history of subarachnoid hemorrhage developed left hemiparesis and was diagnosed with acute cerebral infarction due to right middle cerebral artery occlusion. Mechanical thrombectomy achieved partial reperfusion. DSA and postoperative 3D-CT angiography showed only mild stenosis at the posterior wall of the carotid bulb. However, carotid ultrasonography revealed a membrane-like structure with a lodged thrombus, leading to a diagnosis of a carotid web. Carotid artery stenting was performed to prevent further cerebral embolism, and the postoperative course was uneventful. While digital subtraction angiography and 3D-CT angiography are regarded as the gold standards for diagnosing carotid web, they may only reveal a slight, insignificant filling defect, potentially leading to a missed diagnosis when a large thrombus is present. Carotid ultrasonography is particularly useful in such cases. As revascularization procedures with CEA or CAS are highly effective in lowering the risk of recurrent ischemic stroke in symptomatic CaW, it is crucial to avoid missed diagnoses of symptomatic CaW in ESUS cases, particularly in patients without typical vascular risk factors, through multimodal imaging, including carotid ultrasonography, and to consider revascularization to prevent further stroke recurrence.