Discrepant Imaging Findings in Carotid Web: Challenges in Differentiating from Carotid Stenosis Mimics

Carotid web (CW) is an intimal fibrous thickening, considered a variant of fibromuscular dysplasia. It appears as a shelf-like filling defect in the proximal internal carotid artery (ICA) on angiography and can lead to thrombus formation and embolic stroke. However, distinguishing CW from other carotid pathologies, such as ICA stenosis (ICAS), can occasionally be challenging. A 66-year-old man presented after a motor vehicle accident and was found to have an acute cerebral infarction. Initial computed tomography angiography (CTA) suggested mild ICAS, and carotid ultrasound indicated a non-mobile plaque. Despite anticoagulation, he experienced recurrent strokes, leading to escalation of antithrombotic therapy. Digital subtraction angiography (DSA) later showed mild ICAS with contrast enhancement, suggesting intraplaque hemorrhage. Further imaging, including MRI plaque imaging and superb microvascular imaging (SMI) ultrasound, also pointed to an unstable plaque. Given persistent embolic events, carotid endarterectomy was performed, revealing a CW with an associated thrombus. Retrospective ultrasound review indicated thrombus rather than plaque, and discrepancies between CTA and DSA findings suggested thrombus progression, further supporting CW as the culprit. CW can mimic ICAS and may be overlooked. Changes in imaging over time may suggest thrombus formation. Advanced carotid ultrasound techniques, such as SMI, may aid in distinguishing CW from ICAS.