Recognizing subtle near-occlusion in carotid stenosis patients: a computed tomography angiographic study

Introduction: Near-occlusion of the internal carotid artery (ICA) is a significant luminal diameter (LD) reduction beyond a tight atherosclerotic carotid stenosis (CS). Recognition of even subtle near-occlusions is essential to prevent underestimation of the stenosis degree. Our goal was to investigate the prevalence of near-occlusion among CS patients using a single standard criterion to facilitate its recognition, even when distal ICA LD reduction is not visually evident in computed tomography angiography (CTA).

Methods: We analysed carotid artery CTAs of 467 patients with moderate-to-severe CS scheduled for endarterectomy. We performed measurements of the bilateral distal ICA LDs from thin axial source images and utilized a 1.0 mm intra-individual side-to-side distal ICA LD difference to distinguish near-occlusions, based on a previous study, aware of the vagaries of measurement. For analysis stratification, we excluded cases with significant carotid pathology affecting LD measurements.

Results: We discovered 126 near-occlusions fulfilling our criterion of ipsilateral near-occlusion: the mean LD side-to-side difference (mm) with 95% confidence interval being 1.8 (1.6, 1.9) and a standard deviation of 0.8 mm. Among the 233 cases not meeting our near-occlusion criterion, we found 140 moderate (50-69%) and 93 severe (70-99%) ipsilateral stenoses.

Conclusion: The utilization of 1.0 mm cut-off value for the intra-individual distal ICA LD side-to-side difference to distinguish atherosclerotic ICA near-occlusion leads to a relatively high incidence of near-occlusion. In CTA, recently suggested to be used for near-occlusion diagnosis, a discriminatory 1.0 mm cut-off value could function as a pragmatic tool to enhance the detection of even subtle near-occlusions.