Microsurgical Bypass for Complex Intracranial Aneurysms in the Endovascular Era: Insights from a High-Volume Referral Center

Background/Objectives: Endovascular treatment has become the primary treatment for intracranial aneurysms, yet direct bypass surgery remains an option in selected cases where standard approaches fail. This study aims to evaluate the role, indications, and outcomes of bypass surgery for intracranial aneurysm management in the current endovascular era. Methods: A single-center retrospective analysis was conducted on consecutive cases who underwent direct intracranial bypass surgery for intracranial aneurysms between 2015 and 2024. Data on demographics, aneurysm characteristics, indications, bypass type, patency, and clinical outcomes (using the modified Rankin Scale) were collected. Results: Of the 101 bypasses performed between 2015 and 2025, 25 were used for complex aneurysm cases. Intracranial bypass was necessary in as many as 5% of all microsurgical aneurysm repairs in 2023 and 10% in 2024. Bypass surgery was indicated in young patients with complex aneurysms not amenable to endovascular therapy (45%) and in 20% of the cases for recanalized aneurysms after previous endovascular repair. Intraoperative and postoperative bypass patency was confirmed for all patients except one case due to ongoing malignant brain swelling after an ongoing infarction. At follow-up, 87% of patients, with both ruptured and unruptured aneurysms, had a good outcome (mRS ≤ 2), and all patients had a patent bypass. Permanent morbidity was observed in 5% and procedure-related mortality in 0%. Conclusions: While bypass surgery constitutes a minority of intracranial aneurysm treatment by volume, its role in intracranial aneurysm repair is crucial and relevant in response to the evolving complexity of aneurysms. Further refinement of techniques is necessary.