Methodological Quality and Overlap of Systematic Reviews Comparing Carotid Endarterectomy versus Carotid Artery Stenting in Symptomatic Contralateral Carotid Occlusion: An Overview of Reviews.

BACKGROUND: Symptomatic contralateral carotid occlusion (CCO) is considered a high-risk scenario for carotid revascularization, yet the comparative evidence for carotid endarterectomy (CEA) versus carotid artery stenting (CAS) is largely derived from observational data and repeatedly synthesized in systematic reviews. This research aimed to assess reviews appraising the methodological quality of these evidence syntheses and quantify overlap of included primary studies. METHODS: PubMed and Embase were searched (June 2025) for systematic reviews and meta-analyses comparing CEA versus CAS in adults with symptomatic CCO or reporting extractable symptomatic CCO subgroup data. Two reviewers independently screened studies, extracted data, and assessed methodological quality using AMSTAR-2. Overlap among primary studies across reviews was evaluated using the corrected covered area (CCA). RESULTS: Nine systematic reviews and meta-analyses (published from 2008 to 2021) derived from 86 unique primary studies were included. Overall confidence in review findings was poor: 8 (88.9%) were rated critically low and 1 (11.1%) low by AMSTAR-2. Major limitations included lack of protocol transparency, incomplete reporting of search strategies, absence of excluded-study lists, and insufficient integration of risk-of-bias assessments into interpretation. Across the 86 unique primary studies, the overall CCA was 16.7%, indicating high overlap in the evidence base. Clinical outcome reporting was heterogeneous and often lacked extracted raw event rates. Across reviews, no consistent, methodologically robust superiority of CEA or CAS was demonstrated. CONCLUSIONS: The secondary evidence comparing CEA and CAS in symptomatic CCO is dominated by low-confidence reviews and overlapping assessed evidence from observational cohorts. Future comparative studies and systematic reviews should prioritize standardized outcome reporting, transparent methods, and explicit management of overlapping primary evidence.Clinical ImpactThis overview shows that existing comparisons of CEA versus CAS in symptomatic contralateral carotid occlusion rest on weak, repetitive evidence. Most reviews scored poorly on AMSTAR-2, and the same retrospective studies were reused across multiple reviews, so agreement between them does not mean the findings are truly confirmed. For clinicians, this means current data cannot support choosing one procedure over the other for this high-risk group. Decisions should still be based on the patient's anatomy, surgical risk, and the treating team's experience. Higher-quality, independent studies and more transparent reviews are needed to clarify this question.