Computed tomography angiography evaluation of internal carotid artery free-floating thrombus—single-center diagnosis, false-positives, and follow-up

Abstract

The incidence and management of free-floating thrombus (FFT), also known as intraluminal carotid thrombus, within the internal carotid artery (ICA) are currently unknown. The first case series documenting FFT was published in 1966 [1]. There have been numerous case series publications describing FFT using various modalities mostly including angiography, duplex ultrasound (DU), and more recently computed tomography (CT). Based on retrospective studies, its incidence is estimated to be between 0.4–0.7 % and 0.05 % at cerebral angiography and DU, respectively [2–4]. A more recent single-center retrospective analysis using CT angiography (CTA) quoted the incidence at 3.1 % [5]. With current guidelines for imaging of acute stroke and transient ischemic attack, CTA and magnetic resonance imaging angiography are more frequently being performed in the urgent setting [6]. More than 90 % of patients with FFT develop neurologic sequelae [7]. The “donut sign” has been used to describe the appearance of FFT in the axial plane on CTA [5]. Further characterization of FFT is possible with multiplanar reformatted images and may help distinguish FFT from other mimickers. We present the CTA findings of FFT and describe its potentially unstable clinical course and its resolution on imaging after treatment. Potential false-positives, including complex ulcerated plaque, will be discussed.