Endovascular coiling of very small unruptured intracranial aneurysms (≤ 3 mm) is feasible and associated with a low complication rate, high rates of good functional outcomes, and durable angiographic occlusion.
The study cohort of 116 patients with very small unruptured intracranial aneurysms (VSUIAs) was predominantly female with a mean age in the early 50s.
The mean aneurysm diameter was 2.66 mm and mean neck diameter was 2.1 mm among treated VSUIAs.
Adjunctive devices were used in a substantial minority of cases, with stent-assisted coiling being more common than balloon-assisted coiling.
The thromboembolic event rate was low at 1.7%, with no symptomatic thromboembolic events recorded.
The majority of patients achieved good functional outcomes at clinical follow-up, with a low all-cause mortality rate.
Adequate angiographic occlusion was achieved in the majority of patients at angiographic follow-up.
This research suggests that endovascular coiling — a minimally invasive procedure where tiny platinum coils are inserted into a brain aneurysm to seal it off from blood flow — can be safely performed on very small brain aneurysms (3 millimeters or smaller) that have not yet ruptured. In a study of 116 patients treated across multiple centers, serious complications were rare: fewer than 2% of patients had a blood clot-related event, and less than 1% experienced a rupture during the procedure, with no deaths during surgery. Nearly 94% of patients who had follow-up visits were functioning well in daily life, and over 86% showed durable sealing of the aneurysm on imaging at about six months after treatment. This matters because very small unruptured brain aneurysms present a difficult decision for doctors and patients. While the lifetime risk of rupture is relatively low, a rupture can be catastrophic. Until now, there has been limited evidence on whether treating these tiny aneurysms with coiling is worth the procedural risk. This study, drawing from a multicenter registry, provides some of the most systematic data available suggesting the procedure is technically feasible and carries a low rate of serious harm in selected patients. This research suggests that for carefully selected patients whose aneurysms have features that make rupture more likely — such as certain shapes or locations — endovascular coiling may be a reasonable option. However, the authors caution that larger prospective studies are still needed to better define which patients are most likely to benefit, since this was a registry-based analysis and not a randomized controlled trial.
Ashouri Y, Tariq Z, AlMajali M, Kareem M, Nguyen T, Alsarhan M, et al.. (2026). Safety, efficacy, and angiographic outcomes of endovascular coiling for very small unruptured intracranial aneurysms (≤ 3 mm): subgroup analysis of the ECOSA registry.. Frontiers in neurology. https://doi.org/10.3389/fneur.2026.1916793