Near-Total Internal Carotid Artery Occlusion: A Critical Consideration in Carotid Endarterectomy

Carotid endarterectomy (CEA) remains a cornerstone for preventing recurrent ischemic stroke in symptomatic carotid artery stenosis (CAS) of 50-99%. Meta-analyses of pivotal trials (NASCET, ECST, VA) demonstrate that CEA combined with best medical therapy (BMT) reduces 3-year stroke risk from approximately 20% to 3%, with maximal benefit in:

High-grade stenosis (70-99%), particularly when performed ≤2 weeks post-symptoms [1,2]

Women with 50-69% stenosis, where benefit is time-sensitive (≤6 weeks) [3].

Defining Near-Occlusion

Near-occlusion refers to severe stenosis (>95%) with distal lumen collapse due to hemodynamic compromise, often mimicking total occlusion. While historically diagnosed via catheter arteriography (showing delayed internal carotid artery [ICA] filling or early external carotid artery [ECA] collateral flow), contemporary imaging (ultrasound, CTA/MRA) identifies:

“String Sign”: Thread-like residual lumen with high proximal velocities but distal flow reduction [4]

Post-Stenotic ICA Collapse: Distal ICA diameter smaller than the ECA [4].

*Note: NASCET recommends using contralateral ICA diameter for stenosis measurement in near-occlusion due to underfilling of the distal ICA [5].

In routine practice and multidisciplinary team (MDT) discussions, near-total occlusion is frequently overlooked during CEA candidacy assessment. Surgical intervention is often offered without emphasizing unique considerations highlighted in NASCET and ECST trials, potentially leading to harmful outcomes [6].

Why Near-Occlusion Matters

Lower Stroke Risk: Transcranial Doppler studies show reduced emboli due to sluggish flow (5-year stroke risk: 25% → 8% with post-stenotic collapse) [7].

Limited CEA Benefit: Modest early benefit within first 2 years post-CEA • No sustained advantage at 5-year follow-up • Contrasts with persistent long-term benefit in 70-99% stenosis [8].

Diagnostic Pitfalls

Imaging Limitations: Collapsed distal ICA may underestimate stenosis severity [9].

Flow Artifacts: Low-velocity Doppler signals mimic total occlusion [9].

Atypical Velocity Profiles: Absence of high-velocity signals typical of moderate-severe stenosis [9] (Table 1).

Table 1:Diagnostic Criteria for Near-Occlusion.

Therapeutic Delay: Misdiagnosis as total occlusion may inappropriately exclude CEA candidates [10]. • Technical Complexity: Collapsed vessels increase perioperative thrombosis/dissection risks [10].

Advanced Imaging: Confirm near-occlusion via contrast-enhanced MRA/CTA or digital subtraction angiography (DSA). • Identify post-stenotic collapse (ICA < ECA diameter) [4].

Ultrasound Optimization: Deploy power Doppler or contrast-enhanced ultrasound for low-flow states [9]. • Systematically trace ICA to distal segments [9].

Multidisciplinary Collaboration: Mandate MDT consensus (vascular neurology, radiology, surgery) [6].

Individualized Decision-Making: For symptomatic patients (TIA/stroke in territory), balance revascularization feasibility against reduced benefit [11].

Conclusion

While CEA may be considered for near-occlusion, clinicians must: • Recognize its distinct pathophysiology and imaging hallmarks [5]. • Counsel patients regarding reduced benefit compared to highgrade stenosis [6]. • Adopt tailored approaches balancing individual risk and technical feasibility [11].

None.

No conflicts of interests.

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