Introduction The off-label use of flow diverting stents (FDS) for treating cerebral aneurysms in small distal vessels is increasing with encouraging results. Data directly addressing the parent vessel size are still scarce.

Aim of Study Our aim was to evaluate the safety and efficacy of FDS placement in anterior and posterior circulation aneurysms with parent arteries ≤ 2 mm in a real-world representative setting.

Methods We retrospectively reviewed patients treated with FDS at the three participating university hospitals between 2009 and 2021. The inclusion criteria were the placement of at least one FDS in a parent vessel with a maximum diameter of 2 mm or less. The primary clinical safety endpoint was the absence of death, major or minor symptomatic stroke, transient ischemic attack and procedure-related intracranial hemorrhage. Clinical outcome was assessed using the modified Rankin Scale (mRS) score at the 1-year follow-up. The primary efficacy endpoint was complete and near-complete occlusion at the 1-year follow-up.

Results We identified 55 patients harboring 56 aneurysms. The primary clinical safety endpoint was obtained in 93% of cases. The hemorrhagic and thromboembolic complication rates were 4% and 9%, respectively. No patient died or had a relevant discrepancy at the pre- and post-treatment mRS. The primary efficacy endpoint was reached in 80% of cases.

Conclusion The use of FDS in vessels ≤ 2 mm is technically feasible with good aneurysm occlusion rates and an acceptable safety profile. Nevertheless, it is essential to be aware of the of the main complications associated when operating in small diameter vessels.

Disclosure of Interest Nothing to disclose.