Risk stratification and treatment outcomes after surgical treatment of 0unruptured intracranial aneurysms: a single-center retrospective review

Purpose Management of unruptured intracranial aneurysms (UIAs) requires weighing rupture risk against treatment risk. As endovascular techniques have evolved, microsurgical intervention has become increasingly concentrated at high-volume centers and reserved for complex cases, potentially representing a higher-risk endeavor than reflected in earlier series. A contemporary evaluation of patient and aneurysm-related features associated with surgical risk and postoperative outcomes is needed. Methods We conducted a single-centre retrospective review of 404 UIAs across 347 patients treated between 1998–2024 at TWH. Demographics, aneurysm characteristics, treatment details, and functional outcome (modified Rankin Scale [mRS] at 4–6 weeks) were recorded. Multivariable Firth penalized logistic regression identified factors associated with postoperative dependency (mRS ≥ 3). Results Aneurysm size greater than 1 cm was independently associated with worse postoperative outcomes (OR 2.4, 95% CI 1.2–4.8, p = 0.013), irrespective of morphology, location, or comorbidity. Minimally invasive craniotomies correlated with shorter hospital stays (2.5 ± 1.5 vs 4.4 ± 2.9 days) and lower dependency rates (2.4% vs 17.0%, p < 0.001) than standard craniotomies. Bypass procedures (27 cases) carried greater stroke rates (29.6% vs 6.4%, p < 0.001) and poorer outcomes (22.2% vs 6.4%, p = 0.01) than clipping. Overall mortality was 2.0%. Conclusions Among surgically treated UIAs, size > 1 cm was associated with functional dependency, irrespective of location, morphology, or comorbidities, while most aneurysms under 1 cm remained functionally independent regardless of other factors. These findings provide a contemporary, risk-stratified framework to guide patient selection and multidisciplinary counselling.