Duplex ultrasound in severe carotid stenosis: diagnostic performance for differentiating near-occlusion subtypes from...

Carotid near-occlusion (CNO) is a subtype of severe carotid stenosis characterized by partial or complete distal internal carotid artery (ICA) collapse. Its diagnosis currently relies on angiographic imaging, and no validated duplex ultrasound (DUS) criteria exist. We aimed to assess the utility of DUS in distinguishing conventional high-grade stenosis (HGS), CNO without, and CNO with full collapse.

We retrospectively included patients with > 80% NASCET stenosis on DUS (2012-2021) who underwent CTA, MRA, or DSA within 3 months. DUS parameters were compared across groups defined by angiographic classification using uni- and multivariable analyses.

Among 78 patients, 21 had HGS, 34 CNO without, and 23 CNO with full collapse. DUS agreed with angiographic classification in 54%, with CNO without full collapse often misclassified as HGS (85%). Velocity-based DUS metrics could not reliably distinguish CNO without full collapse from HGS. However, CNO with full collapse was distinguishable based on stenotic and distal peak-systolic and end-diastolic velocities and derived ratios (AUCs 0.70-0.76). Diameter-based metrics distinguished HGS from both CNO types: distal ICA < 3.15 mm (AUC 0.79) and ICA/ECA ratio < 0.98 (AUC 0.78). Multivariable models increased discriminatory performance (AUC 0.82).

Velocity-based DUS metrics cannot reliably distinguish HGS from CNO without full collapse, representing a key clinical challenge. Although DUS-derived metrics were associated with angiographically defined CNO with full collapse, overall diagnostic gain was modest and additional imaging will often remain necessary. Nevertheless, DUS remains useful for follow-up, as hemodynamic changes may indicate evolving distal collapse.