AUTHOR=Ashouri Yazan , Tariq Zain , AlMajali Mohammad , Kareem Mustafa Abdul , Nguyen Thanh N. , Alsarhan Mo'ath , Chaudhari Amit , Ramirez-Abreu Darwin , Bhattarai Anjan , Nogueira Raul G. , Levy Elad I. , Xavier Andrew , Linfante Italo , Gupta Rishi , Hsu Daniel P. , Dion Jacques E. , Cawley C. Michael , Tong Frank C. , Mueller Nils , Edgell Randall C. , Norbash Alexander , Zaidat Osama O. 
  
TITLE=Safety, efficacy, and angiographic outcomes of endovascular coiling for very small unruptured intracranial aneurysms (≤ 3 mm): subgroup analysis of the ECOSA registry
  
JOURNAL=Frontiers in Neurology
  
VOLUME=Volume 17 - 2026
  
YEAR=2026
  
URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2026.1916793
  
DOI=10.3389/fneur.2026.1916793
  
ISSN=1664-2295
  
ABSTRACT=IntroductionVery small unruptured intracranial aneurysms (VSUIAs) measuring ≤ 3 mm represent a unique clinical challenge, balancing the low but non-negligible lifetime risk of rupture against the procedural risks of endovascular intervention. This study reports the safety, efficacy, and angiographic outcomes of endovascular coiling for VSUIAs from the ECOSA (Endovascular Coiling of Small Aneurysms) multicenter registry.MethodsWe performed a subgroup analysis of the ECOSA multicenter registry of patients with VSUIAs (maximum diameter ≤ 3 mm) who underwent endovascular coiling. Patient demographics, aneurysm characteristics, procedural details, periprocedural complications, clinical outcomes (modified Rankin Scale; mRS), and angiographic follow-up data were analyzed.ResultsA total of 116 patients with 116 VSUIAs underwent endovascular coiling. The mean age was 52.3 years (SD 12.1), and the majority were female (75.0%). The mean aneurysm diameter was 2.66 mm (SD 0.44) and mean neck diameter was 2.1 mm (SD 0.87). Most aneurysms were discovered incidentally (78.4%). Balloon-assisted coiling was used in 14.7% and stent-assisted coiling in 23.3% of cases. The thromboembolic event (TEE) rate was 1.7%, with no symptomatic events. Intraprocedural rupture occurred in 0.9% of cases with no intraprocedural mortality. Among 98 patients with clinical follow-up (median 7.75 months), 93.9% of patients achieved good functional outcomes (mRS 0–2), and all-cause mortality rate was 1.0%. Among 80 patients with angiographic follow-up (median 6 months), adequate occlusion (RROC I–II) was achieved in 86.3%.DiscussionEndovascular coiling of VSUIAs ≤ 3 mm is feasible and associated with a low complication rate, high rates of good functional outcomes, and durable angiographic occlusion. These findings support the safety of elective intervention in carefully selected patients with high-risk morphological or clinical features. Larger prospective studies are needed to define optimal patient selection criteria for VSUIAs.