OBJECTIVE: Blister aneurysms of the internal carotid artery (ICA) have high associated mortality rates and are challenging due to their friable wall and poorly defined neck. Microsurgical and endovascular treatment options have been suggested, including bypass of the parent vessel to exclude the aneurysm. The goal of this study was to evaluate the safety and efficacy of microsurgical versus endovascular interventions. Additionally, for patients treated with open surgery, the outcomes of bypass were compared to nonbypass techniques. METHODS: Three databases were systematically queried for primary studies comparing microsurgery to endovascular therapy and assessing bypass versus nonbypass treatment modalities for blister aneurysms of the ICA. All relevant studies published between 2000 and 2023 were eligible for inclusion. All articles were screened against title and abstract by 2 authors, as were those eligible for full-text assessment. Ultimately, relevant data from all included studies were pooled for meta-analysis in which the Mantel-Haenszel method with random-effects modeling was used. RESULTS: Among the 504 cases reported across 24 studies, 182 (35.1%) blister aneurysms of the ICA were surgically treated, whereas 337 (64.9%) involved endovascular treatment. There were 235 (46.6%) female patients in the cohort. Functional outcomes were comparable between groups, with 83% of surgically treated patients and 85% of endovascularly treated patients achieving a favorable outcome (p >
0.05). Among the 7 studies (178 patients) comparing bypass to nonbypass microsurgery, rates of postoperative bleeding, ischemic infarct, vasospasm, recurrence, favorable outcomes, and mortality were comparable for bypass (n = 54, 30.3%) and nonbypass groups (n = 124, 69.7%). CONCLUSIONS: Blister aneurysms of the ICA are rare intracranial aneurysms that are difficult to treat with microsurgical and endovascular techniques. Considering only patients treated with open surgery, there appears to be no significant difference in complication profile or functional outcomes between patients undergoing bypass or alternative microsurgical techniques. However, it must be noted that the complex nature of bypass procedures means that much of the data granularity is lost on meta-analysis, suggesting that additional investigations comparing bypass to other open microsurgical techniques may be merited. Similarly, future studies should determine the limitations of dual antiplatelet therapy in endovascular treatment and the efficacy of different numbers and types of overlapping, flow-diverting devices.