Efficacy and Safety of Extracranial-Intracranial Bypass Surgery for Posterior Circulation Aneurysms: A Systematic Review and Single-Arm Meta-Analysis

Introduction: Treating posterior circulation aneurysms poses challenges, and extracranial to intracranial (EC-IC) bypass is an option of cerebrovascular surgeon’s armamentarium when clipping or endovascular approach are not feasible. However, the safety and efficacy of this approach for posterior circulation aneurysms remain unclear. The objective of the study was to assess the safety and efficacy of EC- IC bypass in these aneurysms.

Methods: Adhering to PRISMA guidelines, we conducted a systematic review on EC-IC revascularization in posterior circulation aneurysms. Included studies had at least four patients, and reported data on mortality, patency, complications, or clinical outcomes. Favorable clinical outcomes were defined as mRS below 3 or GOS above 3, and complications were considered any issues related to the bypass procedure. Statystical analysis was performed on the software R studio.

Results: From 3,036 articles reviewed, 22 studies involving 196 patients who underwent 210 EC-IC bypass procedures for posterior circulation aneurysms were selected. The median follow-up period of 14 studies was 31.66 months (6 - 61 months). Thirty-four aneuryms (34.3%) were ruptured, and 65 (65.6%) were unruptured, with information available for 99 patients. Final follow-up indicated a high bypass patency rate of 96% [95% CI: 91% - 100%; I2 = 12%], with a mortality rate of 5% [95% CI: 1% - 9%; I2 = 0%]. Additionally, 83% [95% CI: 70% - 96%; I2 = 77%] of patients showed good outcomes at the last follow-up. Complications were observed in 40% [95% CI: 26% - 55%; I2 = 80%]. Heterogeneity was associated with specific studies.

Conclusion : EC-IC bypass procedures are a viable treatment option for posterior circulation aneurysms when traditional approaches are not suitable, with high bypass patency rates and favorable clinical outcomes. However, complications, especially neurological deficits, exist. Further research is needed to confirm results and understand underlying causes.