# Carotid near-occlusion diagnostics and its consequences: A systematic review

## TL;DR

This paper reviews the challenges in diagnosing carotid near-occlusion and highlights the importance of better diagnostic methods like PC-MRI to improve patient outcomes.

## Contribution

The study identifies PC-MRI as a highly accurate diagnostic method for CNO and emphasizes its potential to change clinical perceptions and practices.

## Key findings

- PC-MRI is highly sensitive and specific for diagnosing CNO when used with blinded assessments.
- CNO is more common than previously thought, especially in studies with good diagnostics.
- Symptomatic CNO does not benefit from revascularization, particularly the moderate subtype.

## Abstract

To summarize carotid near-occlusion (CNO) diagnostics and its consequences on epidemiology and management.

A systematic search of PubMed using 19 known synonyms for CNO was performed. Diagnostic analyses of CNO were assessed. Epidemiological and management analyses were based on how the CNO diagnostics was conducted, with diagnostics resembling large trials considered “good.”

CNO can be diagnosed with several modalities and approaches (interpretation or measurements). Interpretation of angiography is the reference standard but is not feasible for routine use. Of feasible methods, flow measurements with phase-contrast magnetic resonance imaging (PC-MRI) were considerably better than other alternatives when assessed blinded: 90%–100% sensitive and 99%–100% specific and inter-rater kappa 0.98–1.0. CNO was consistently common (30% of ⩾50% stenosis) in studies with “good” CNO diagnostics but was also often described as rare. Symptomatic CNO have no benefit with revascularization in studies with “good” CNO diagnostics, which foremost applies to the moderate subtype (without full collapse). The more severe CNO subtype (with full collapse) seems to have a very high risk of stroke within the first 2 days, but revascularization performed sufficiently early to prevent this has never been assessed.

CNO diagnostics is difficult and that CNO is perceived as rare by many is likely due to poor diagnostics. Such poor diagnostics also likely result in unnecessary surgeries for many symptomatic CNOs.

CNO is a common variant of carotid stenosis. New diagnostic methods (especially PC-MRI) should be introduced, possibly after validation of its prognostic impact in a randomized trial.

Graphical abstract