Abstract 448: Treatment Modalities and Outcomes Among Patients with <3mm and ≥3mm Intracranial Aneurysms
Authors: Zauner A. , Zikakis I. , Korbakis G. , Froehler M. T. 
Published: January 2025

Introduction
Treatment of very small, ruptured, and symptomatic intracranial aneurysms (IA) remains challenging, despite advances in endovascular and surgical techniques. We summarized outcomes for very small (<3mm) vs. larger (≥3mm) IA in patients who underwent treatment.

Methods
Prospectively collected data from adults who underwent treatment for an IA at the Stroke and Neurovascular Center of Central California between August 2018 and August 2022 were retrospectively reviewed. Demographics, medical history, aneurysm, and procedural characteristics were recorded. Coiling procedures used the Optima Coil (Balt USA). Flow diverters included Pipeline (Medtronic, Inc.), Surpass Evolve (Stryker) and Synergy (Boston Scientific). Outcomes were post‐procedure Raymond‐Roy Occlusion Classification (RROC), retreatment, intraoperative complications, vasospasm, and mortality. Mann‐Whitney U tests compared continuous and ordinal baseline characteristics. Fisher's exact test compared dichotomous baseline variables and safety outcomes. Ordinal regressions compared RROC scores between groups, with adjustment for follow‐up time for final RROC scores. Subgroup analyses were performed among unruptured and ruptured aneurysms.

Results

329 patients with 367 aneurysms were included, of which 163 were <3mm and 204 were ≥3mm. Median age was 59 years (IQR: 48‐67) for the <3mm group and 66 years (IQR: 55‐74) for the ≥3mm group (p<0.001). Aneurysms were ruptured in 39.3% of the <3mm group and 27.0% of the ≥3mm group (p=0.01). Interventions included coiling (132, 36.0%), stent‐assisted coiling (113, 30.8%), clipping (46, 12.5%), flow diversion (69, 18.8%), NBCA (3, 0.8%), and coiling + flow diversion (3, 0.8%) (
Table
1). There were no statistically significant differences in RROC or safety outcomes between <3mm and ≥3mm aneurysms, either in the overall population or within unruptured and ruptured subgroups. However, <3mm aneurysms tended to have better RROC scores post‐procedure (cOR=5.52, p=0.12) and at last follow‐up (cOR=2.41, p=0.20), as well as lower retreatment rates for unruptured aneurysms (OR=0.29, p=0.12). For ruptured aneurysms, post‐procedure RROC scores and retreatment rates were similar, but smaller aneurysms tended to have better predicted RROC scores at the last follow‐up (cOR=2.02, p=0.33). Complications, vasospasm, and mortality rates were similar between aneurysm size groups, both for unruptured and ruptured aneurysms.

Conclusion
Most patients achieved complete occlusion, regardless of aneurysm size, and did not require retreatment. Treatment outcomes do not differ significantly between very small aneurysms and those >3mm.

Table
1:
Procedural and Outcome Characteristics

Results for RROC scores and retreatment are presented as predicted probabilities with 95% confidence intervals. Predicted probabilities for RROC scores were derived from ordinal regressions, while those for retreatment were obtained from logistic regressions. Interventions and safety outcomes, including complications, vasospasm, mortality at 1 year, and mortality at any timepoint, are presented as raw data with n/N (percentage of total). P‐values for efficacy outcomes related to RROC and retreatment were calculated using two‐sided z‐distributions following regression analyses, and p‐values for safety outcomes were determined using Fisher's exact test. Complications included loss of coil, leakage, compromised M2 branch, repositioned clip, and direct ccf.