Closer matching between flow diverter diameter and parent artery diameter is associated with improved aneurysm occlusion.

Background: Selecting the flow diverter (FD) size is key to treatment outcomes in unruptured intracranial aneurysms. However, the impact of differences between the nominal and actual deployed device sizes on aneurysm occlusion is not fully understood. This study retrospectively evaluated the relationship between FD size and aneurysm occlusion. Methods: We retrospectively analyzed 54 patients with unruptured intracranial aneurysms who underwent FD placement at our institution from March 2023 to March 2025, where both length (Length_D) and diameter (Size_D) discrepancies were evaluated. Devices used were a Flow Redirection Endoluminal Device in 31 cases and a Pipeline Embolization Device in 23 cases. Length_D is the difference between the nominal device length and actual deployed length, while Size_D is the difference between the nominal device diameter and actual deployed diameter. The primary endpoint was aneurysm occlusion at 6 months, assessed using the O'Kelly-Marotta (OKM) scale. Adequate occlusion was defined as OKM grades C-D and incomplete occlusion as OKM grades A-B. Patients were divided into adequate and incomplete occlusion groups, and Length_D and Size_D were compared. Results: Adequate occlusion was achieved in 68.5% of patients. The mean Length_D was 2.9 ± 3.9 mm in the adequate occlusion group and 6.7 ± 5.1 mm in the incomplete occlusion group, with a significantly greater value in the incomplete occlusion group. Conclusion: Greater FD elongation post-deployment may be linked to lower aneurysm occlusion rates at 6 months. Choosing an FD size that matches the parent vessel diameter is crucial for optimal occlusion.