Efficacy of Mechanical Thrombectomy in Acute Ischaemic Stroke Due to Large Vessel Occlusion of the Internal Carotid Artery: A Comprehensive Systematic Review and Meta-Analysis of Randomised Controlled Trials and Primary Studies

Background: Occlusion of the internal carotid artery (ICA) is among the most severe phenotypes of large vessel occlusion (LVO) stroke, yet ICA-specific evidence on mechanical thrombectomy (MT) is dispersed across trial subgroups, registries and case series. We aimed to quantify the efficacy and safety of MT in acute ischaemic stroke (AIS) due to ICA occlusion and to explore effect modification by occlusion pattern, tandem-lesion management and bridging intravenous thrombolysis (IVT). Methods: The study strictly adhered to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 guidelines. Eligible designs were randomised controlled trials (RCTs, including secondary and pooled patient-level analyses of RCTs), comparative studies, cohorts and case series; systematic reviews were excluded from synthesis. The primary outcome was 90-day functional independence (modified Rankin Scale [mRS] 0–2). Random-effects (REML) models with Hartung–Knapp–Sidik–Jonkman sensitivity analyses were used; proportions were pooled on the logit scale. Risk of bias was assessed with RoB 2, ROBINS-I and the JBI case-series checklist, and certainty with GRADE. Results: Thirty-three reports (101 outcome-specific datasets) were included. In 8 datasets comparing MT with best medical treatment (BMT; 1,788 patients), MT increased functional independence (OR 2.17, 95% CI 1.39–3.38; I² = 57%; absolute risk difference +11.8%; number needed to treat ≈ 9). The effect was largest in intracranial ICA occlusion (OR 2.97, 1.88–4.67) and in RCT-derived datasets (OR 3.01, 1.96–4.63), but was not statistically significant in isolated cervical ICA occlusion (OR 1.30, 0.94–1.79; p for subgroup difference = 0.003). MT produced a favourable ordinal mRS shift (common OR 1.73, 1.19–2.51) without a significant difference in mortality (OR 0.86, 0.58–1.28) or symptomatic intracranial haemorrhage (sICH; OR 1.91, 0.73–4.98). Across MT-treated cohorts, pooled successful reperfusion was 78.7% (73.1–83.4), mRS 0–2 43.0% (37.6–48.6), sICH 5.9% (4.3–8.0) and mortality 18.5% (15.1–22.4), with the highest mortality in intracranial ICA occlusion (24.9%). In tandem lesions, emergent carotid artery stenting was associated with higher functional independence (OR 1.41, 1.23–1.61) without a significant increase in sICH (OR 1.18, 0.92–1.51). Prior IVT showed no significant overall association with outcome (OR 1.49, 0.82–2.71), with discordance between RCT-derived (OR 0.63) and observational (OR 2.15) estimates. Conclusions: MT substantially improves functional outcome in AIS due to ICA occlusion, particularly intracranial ICA occlusion, supported by moderate-certainty RCT-derived evidence. Benefit in isolated cervical ICA occlusion remains uncertain, and emergent stenting of tandem cervical lesions appears favourable on low-certainty evidence. Dedicated randomised trials stratified by ICA occlusion pattern are warranted.