One-year outcomes of unruptured intracranial aneurysms < 5 mm in a Latin American multicenter cohort of 1,098 patients.

Unruptured intracranial aneurysms smaller than 5 mm represent a frequent clinical dilemma, particularly in regions where local outcome data are scarce. Evidence from Latin American populations remains limited, despite differences in case complexity, treatment strategies, and healthcare systems. We conducted a multicenter, retrospective observational study including adult patients with unruptured intracranial aneurysms < 5 mm treated between 2017 and 2023 at eight specialized centers in five Latin American countries. Clinical, morphological, and treatment-related variables were analyzed. One-year mortality and functional outcome were assessed using the modified Rankin Scale (mRS). Multivariable logistic regression models were used to identify independent predictors of mortality and poor functional outcome (mRS ≥ 3). A total of 1,098 patients were included (mean age 57.6 years; 55% female). Endovascular treatment was performed in 68%, surgical clipping in 5%, and conservative management in 27%. The overall treatment-related complication rate was 3.5%, with no significant differences between surgical and endovascular modalities. One-year mortality was 3%, and poor functional outcome occurred in 5% of patients. Independent predictors of mortality included age > 65 years (OR 3.62) and in-hospital medical complications (OR 9.45). Poor functional outcome was independently associated with age > 65 years, single antiplatelet therapy (vs. dual antiplatelet therapy), treatment-related complications, and in-hospital medical complications. Functional outcomes and aneurysm occlusion rates were within the range reported in international series. Although most unruptured intracranial aneurysms < 5 mm have a favorable prognosis, a non-negligible risk of mortality and disability persists. Outcomes in this Latin American cohort were comparable to those reported in international series. These findings suggest that outcomes in this cohort are comparable to those reported in international series. However, given the observational design and heterogeneity across centers, these results should be interpreted cautiously and may reflect differences in patient selection, treatment strategies, and institutional experience.