Background and purpose Thromboembolic events are recognized complications of aneurysm coiling.

Objective To identify any protective effects of antiplatelet therapy use before coiling of unruptured aneurysms.

Methods We conducted a meta-analysis of clinical studies published up to February 2019. We included studies reporting symptomatic thromboembolic events (defined as clinical stroke or transient ischemic attacks) in patients who received antiplatelet therapy before coiling of unruptured aneurysms using unassisted coiling, balloon assistance, or multiple microcatheters. We excluded ruptured aneurysms and those treated with stent coiling or flow diverters.

Results We identified 14 studies (2486 patients). All were single-center studies and four were prospective. In three studies with a control (no treatment) arm, the pooled risk ratio for symptomatic thromboembolic events with versus without antiplatelet therapy was 0.33 (95% CI 0.17 to 0.92, p= 0.035). The cumulative risk of symptomatic thromboembolic events with single antiplatelet agents was 5.0% ‘56/1122’ (95% CI 1.6% to 8.4%, I²83.63%), and with dual or multiple agents 2.7% ‘33/1237’ (95% CI 1.0% to 3.0%, I²39.9%). The incidence of diffusion lesions was reported in seven studies. It was 50.5% ‘96/190’ (95% CI 7.3% to 93.9%, I²94.4%) with single agents compared with 43.9% ‘196/446’ (95% CI 25.9% to 61.9%, I²73.4%) with dual or multiple agents.

Conclusion Periprocedural antiplatelet therapy was associated with a low symptomatic thromboembolic event after coiling-only for unruptured aneurysms. However, available evidence is of limited quality with significant heterogeneity, requiring evidence from randomized controlled trials.