Indications and Outcomes of Intracranial Bypass: A Systematic Review and Meta-analysis

Objective: This systematic review and meta-analysis aims to provide an overview of the indications, selection criteria, and outcomes of intracranial direct bypass surgery. Methods: Embase, Ovid Medline, the Web of Science Core Collection, Google Scholar, and Cochrane Central Register of Controlled Trials were searched from inception to February 11, 2025, for original studies reporting indications for bypass surgery including human subjects. Patency, procedure-related neurological complications, postoperative poor clinical outcome, and mortality rates were analyzed using a random-effects model. Pooled prevalence rates and 95% confidence intervals (CIs) were presented. Results: The search yielded 7449 articles of which 5478 remained after removing duplicates. After initial screening, 251 articles remained to be assessed for eligibility based on full-text sifting. Ultimately, 142 articles were included. One hundred six studies reported “steno-occlusive disease” as an indication. Postoperative poor clinical outcome occurred in 9% of the patients (95% CI 5.1–13.0; I² = 78%), and the mortality rate was 3.5% (95% CI 1.6–5.5; I² = 82%). Forty-one studies reported “Moyamoya vasculopathy” as an indication. Postoperative poor clinical outcome occurred in 5.5% of the patients (95% CI 0.6–10.4; I² = 78%), and the mortality rate was 0.6% (95% CI 0.0–1.7; I² = 0%). Seven studies reported “urgent bypass” as an indication, 7 studies “ruptured aneurysm treatment,” and 29 studies “complex unruptured aneurysm treatment.” Conclusions: Despite a decline in indications, intracranial bypass surgery remains a highly relevant option for the treatment of diseases such as Moyamoya vasculopathy, as a salvage option in steno-occlusive disease with hemodynamic compromise, and treatment of aneurysms not amenable to microsurgical or endovascular repair.