Introduction The registry of cerebral aneurysms < 5 mm, known for their low risk of rupture, is significant, given their high incidence globally.

Aim of Study Our study aimed to identify, in small aneurysms (< 5 mm), the potential morphological characteristics, risk factors that can predict the risk of rupture, and the risk or benefit of treating them with endovascular or conservative treatment in ruptured and unruptured intracranial aneurysms.

Methods The medical records of patients with cerebral aneurysms < 5 mm were retrospectively reviewed between January 2014 and December 2022 at two neurovascular centers in Colombia. We evaluated clinical and angiographic outcomes using statistical tests.

Results Two hundred fifty-six patients (425 intracranial aneurysms) were registered in the database. Two hundred and seventy-five were treated with endovascular treatment: 70 ruptured aneurysms and 205 unruptured aneurysms. One hundred fifty intracranial aneurysms underwent conservative treatment (follow-up). Women accounted for 82.1% of cases. Most cases were incidentally diagnosed (83.5%). After a year of follow-up, 87.3% of unruptured and 67.1% of ruptured intracranial aneurysms had an mRS 0 – 2. In the Raymond-Roy occlusion classification, among 101 unruptured intracranial aneurysms embolized were 53 cases class I, and among 66 ruptured intracranial aneurysms embolized, 67.1% were class I.

Conclusion Endovascular therapy for aneurysms < 5 mm appears to be a technically feasible treatment, with satisfactory occlusion rates and few re-treatments at the 12-month follow-up. The complication rates were similar to those reported in studies on small aneurysms.