Differentiating pseudo-occlusion from true occlusion of proximal internal carotid artery in acute ischemic stroke on CT angiography

Abstract

ObjectiveA lack of visualization of the proximal internal carotid artery (ICA) on computed tomography angiography (CTA) in acute ischemic stroke may be caused by an atherosclerotic occlusion or a pseudo-occlusion by a massive thrombus in the ICA. Pseudo-occlusion of the proximal ICA is caused by stagnant flow from a distal ICA occlusion. The purpose of this study aimed to use imaging findings of CTA to differentiate pseudo-occlusions from true occlusions of the proximal ICA. Patients and methodsAll eligible patients undergoing endovascular treatment after CTA from January 2013 to March 2018 were respectively reviewed. Patients with <2 cm of ICA on CTA images were enrolled in this study. CTA images were classified as having a beak, dome, or flat pattern. ResultsOur sample included a total of 66 eligible patients (true occlusion: 31, pseudo-occlusion: 35). The total length of opacification of the proximal ICA in the pseudo-occlusion group was significantly higher compared to that in the true occlusion group (13.9 ± 4.0 vs. 6.1 ± 4.8, p < 0.001). A beak pattern of the proximal ICA on CTA images was significantly higher in the pseudo-occlusion group (82.9% vs. 16.1%, p < 0.001), but a flat pattern was significantly higher in the true occlusion group (58.1% vs. 0%, p < 0.001). Gradual contrast decline of the proximal ICA on CTA images only appeared in the pseudo-occlusion group (51.4%, p < 0.001). ConclusionsOn CTA, imaging patterns of the proximal ICA can be differentiated between true occlusions and pseudo-occlusions.