Endovascular versus Best Medical Treatment for Acute Carotid Occlusion BelOw Circle of Willis (ACOBOW): The ACOBOW Study.

Background Symptomatic acute occlusions of the internal carotid artery (ICA) below the circle of Willis can cause a variety of stroke symptoms, even if the major intracranial cerebral arteries remain patent; however, outcome and safety data are limited. Purpose To compare treatment effects and procedural safety of endovascular treatment (EVT) and best medical treatment (BMT) in patients with symptomatic acute occlusions of the ICA below the circle of Willis. Materials and Methods This retrospective, multicenter cohort study from 22 comprehensive stroke centers in Europe and Asia includes patients treated between January 1, 2008, and December 31, 2022. Functional (modified Rankin Scale [mRS]) and clinical (National Institutes of Health Stroke Scale [NIHSS]) outcomes, safety measures (symptomatic intracerebral hemorrhage), mortality, and procedural complications were assessed. Results A total 354 patients met the inclusion criteria (median age, 72 years [IQR, 60-81 years]; median NIHSS, 13 [IQR, 7-19]). Most frequent occlusions were in the C1 segment (243 of 354; 68.6%). Of 354 patients, 82.2% (291 patients) were administered EVT. In the overall population, favorable outcomes (mRS 0-2), mortality, and symptomatic intracerebral hemorrhage occurred in 40.6% (108 of 266 patients), 25.2% (67 of 266 patients), and 7.1% (25 of 350 patients), respectively. After adjustment, no statistically significant difference in functional outcome was observed (adjusted odds ratio [AOR], 0.82 [95% CI: 0.31, 2.12]; average treatment effect, -12.7%; P = .19) in the EVT compared with BMT group. Symptomatic intracerebral hemorrhage (average treatment effect, -0.28%; P = .95) and mortality did not differ between both groups (average treatment effect, -17.1%; P = .07). EVT resulted in complete recanalization of the occlusion in 80.9% (229 of 283) of cases. Periprocedural distal embolization occurred in 27.8% (81 of 291 patients) and was associated with poor outcomes (AOR, 0.41; 95% CI: 0.18, 0.93; P = .03). Conclusion EVT did not reveal a favorable treatment effect over BMT, and both therapies were safe. EVT had a risk for periprocedural distal embolization associated with poor outcomes. © RSNA, 2025 Supplemental material is available for this article. See also the editorial by Daou and Chaudhary in this issue.