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

Methods Prospectively collected data from adult patients who underwent treatment for an IA between August 2018 and August 2022 were retrospectively reviewed. Patient demographics, medical history, and aneurysm and procedural characteristics were recorded. Coiling procedures used the Optima Coil (Balt USA). Outcomes were intraoperative complications, post-procedural Raymond-Roy Occlusion Classification (RROC), and RROC at mid to long-term follow-up (9–56 months). Mann-Whitney U tests were used to compare continuous and ordinal values. Fisher’s exact binomial test was used to compare dichotomous variables. Logistic regression was performed to compare odds of post-procedural RROC 1 vs. 2, and to compare retreatment rates. Ordinal regression was used to compare RROC at follow-up, accounting for precise follow-up timing as a covariate. Two-sided p-values were extracted from the model results.

Results A consecutive series of 329 patients with 398 IA were included, of which 163/368 (44.3%) were small (<3 mm) and 205/368 (55.7%) were larger (≥3 mm). Treatment modalities for each group are shown in table 1. Patients with <3 mm aneurysms were younger at the start of treatment compared to the ≥3 mm group (median=59 [IQR: 48–67] vs. median=66 [IQR: 55–74], p<0.001). Multiple aneurysms were present in 32.5% of the <3 mm group, and 30.2% of the ≥3 mm group (p=0.652). Family history of aneurysms was present in 16.0% of the <3 mm group and 11.2% in the ≥3 mm group (p=0.217). Aneurysms were ruptured in 42.9% (70/163) of the <3 mm group and 30.2% (62/205) of the ≥3 mm group (p=0.104). There was no difference Hunt & Hess score distribution among ruptured aneurysms (p=0.475). Intraoperative complications occurred in 3.1% of the <3 mm group and 1.5% of the ≥3 mm group (p=0.475). Post-procedure RROC 1 and 2 were achieved in 98.8% (160/162) and 1.2% (2/162) in the <3 mm group vs. 96.7% (197/204) and 3.4% (7/204) in the ≥3 mm group (OR: 2.84, p=0.196). Median RROC follow-up time was 31 months [IQR: 16–40] for the <3 mm group vs. 31 months [17–39.5] for the ≥3 mm group (p=0.983). Distributions of RROC scores 1–3 at mid/long-term follow-up were not significantly different between groups (p=0.255). Retreatment occurred in 5.5% of the <3 mm group and 8.3% of ≥3 mm (p=0.306), within similar timeframes (median=9 months [IQR: 2.5–23], median=8 months [IQR: 4–16], p=0.989). A complete analysis including assessment of causal relationships will be presented at the conference.

Conclusions Smaller IA appear in a younger population, and coiling without flow diversion of <3 mm ruptured and symptomatic aneurysms is as safe and effective as treating ≥3 mm IA using currently available endovascular and surgical modalities.

Disclosures A. Zauner: 1; C; Balt USA. 2; C; Balt USA. I. Zikakis: None. G. Korbakis: None.