Retrospective analysis of outcomes and prognostic factors in patients with subarachnoid hemorrhage from rupture of small intracranial aneurysms: A multicenter study of 421 cases

Objectives: Subarachnoid hemorrhage (SAH) secondary to rupture of aneurysms smaller than 5 mm represents a high-risk clinical condition, even in specialized centers. Despite therapeutic advances, uncertainty persists regarding prognostic factors in this specific subgroup. This study aimed to evaluate 1-year clinical outcomes and identify independent predictors of mortality and poor functional outcome in a Latin American cohort. Materials and Methods: We conducted a multicenter, retrospective, observational study including 421 adult patients with SAH due to rupture of aneurysms ≤5 mm, treated between 2017 and 2023 at eight reference centers across five Latin American countries. Clinical, radiological, anatomical, and therapeutic variables were analyzed. Univariate analyses and multivariate binary logistic regression models were used to identify independent predictors of 1-year mortality and poor functional outcome, defined as modified Rankin Scale ≥3. Results: Mean age was 55.4 years, and 60% of patients were female. Severe SAH (World Federation of Neurosurgical Societies grades 4–5) was present in 32% of cases at admission. One-year mortality was 18%, and 31% of patients experienced a poor functional outcome. In multivariate analysis, independent predictors of mortality included age >65 years, diabetes mellitus, severe SAH, aneurysmal rebleeding, acute hydrocephalus, and the occurrence of medical or treatment-related complications. Poor functional outcome at 1 year was independently associated with age >65 years, prior SAH, severe SAH, aneurysmal rebleeding, acute hydrocephalus, cerebral edema, and in-hospital medical or treatment-related complications. Conclusions: In patients with SAH from ruptured aneurysms smaller than 5 mm, prognosis is primarily driven by initial neurological severity and the development of acute complications rather than by treatment modality. These findings underscore the importance of early risk stratification, prompt complication management, and multidisciplinary care in real-world neurovascular practice, particularly in regions with heterogeneous healthcare resources.