Outcomes of Intracranial-Intracranial Bypass: A Systematic Review and Meta-Analysis

Introduction: The recent increase in publications centered on intracranial-intracranial (IC-IC) bypasses has spotlighted the procedure for complex aneurysms. However, there is no robust evidence regarding its effects. Hence, the authors aimed to assess the outcomes of patients subjected to IC-IC bypass for aneurysms.

Methods: Following PRISMA guidelines, a comprehensive literature exploration was conducted. Criteria for inclusion entailed studies with a cohort of at least four patients having undergone IC-IC bypass for aneurysms, detailing at least one outcome such as patency, clinical outcomes, complications, and procedure-related mortality. For assessing beneficial clinical outcomes, both mRS and GOS were employed. When the study included patients who had undergone extracranial-intracranial (EC-IC) bypass, the authors extracted the patency data to juxtapose it with the results of IC-IC.

Results: Of the 2,509 shortlisted studies, 22 met our inclusion criteria, encompassing 251 patients and 257 IC-IC bypass procedures. The median average duration of follow-up was 27.4 (6 - 65.4) months. The IC-IC bypass procedure exhibited a patency rate of 92% (95% CI: 89% - 96%; I² = 21%). The patency rate of IC-IC and EC-IC bypasses did not significantly differ (0.51(95% CI: 0.18 - 1.50; I² = 0)). In terms of clinical outcomes, 91% of the patients showcased positive results (95% CI: 84% - 99%; I² = 47%), with no discernable disparity between the ruptured and unruptured aneurysm subgroups. After analysis, the occurrence rate for complications was 13% (95% CI: 5% - 21%; I² = 60%). Procedure-related mortality stood at 2% (95% CI: 0% - 4 %; I² = 0%).

Conclusion : IC-IC bypass is a valuable resource for vascular neurosurgeons, offering satisfactory patency and favorable clinical outcomes. Complications, when they occur, are typically non-life-threatening due to minimal procedure-related mortality. Wider integration of this technique in neurosurgical training is vital. Further research is needed to compare IC-IC and EC-IC bypass and comprehend IC-IC's long-term effects.