Treatment of Middle Cerebral Artery Aneurysms with Flow-Diverter Stents: A Systematic Review and Meta-Analysis

BACKGROUND:The safety and efficacy of flow-diversion treatment of MCA aneurysms have not been well-established.PURPOSE:Our aim was to evaluate angiographic and clinical outcomes after flow diversions for MCA aneurysms.DATA SOURCES:A systematic search of PubMed, MEDLINE, and Embase was performed for studies published from 2008 to May 2017.STUDY SELECTION:According to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we selected studies with >5 patients describing angiographic and clinical outcomes after flow-diversion treatment of MCA aneurysms.DATA ANALYSIS:Random-effects meta-analysis was used to pool the following outcomes: aneurysm occlusion rate, procedure-related complications, rupture rate of treated aneurysms, and occlusion of the jailed branches.DATA SYNTHESIS:Twelve studies evaluating 244 MCA aneurysms were included in this meta-analysis. Complete/near-complete occlusion was obtained in 78.7% (95% CI, 67.8%–89.7%) of aneurysms. The rupture rate of treated aneurysms during follow-up was 0.4% per aneurysm-year. The rate of treatment-related complications was 20.7% (95% CI, 14%–27.5%), and approximately 10% of complications were permanent. The mortality rate was close to 2%. Nearly 10% (95% CI, 4.7%–15.5%) of jailed arteries were occluded during follow-up, whereas 26% (95% CI, 14.4%–37.6%) had slow flow. Rates of symptoms related to occlusion and slow flow were close to 5%.LIMITATIONS:Small and retrospective series could affect the strength of the reported results.CONCLUSIONS:Given the not negligible rate of treatment-related complications, flow diversion for MCA aneurysms should be considered an alternative treatment when traditional treatment methods are not feasible. However, when performed in this select treatment group, high rates of aneurysm occlusion and protection against re-rupture can be achieved.

Flow-diverter stents have become a feasible and effective treatment for most intracranial aneurysms, and their indications are constantly extended, including distal aneurysm locations.^1–3 Commonly, middle cerebral artery aneurysms present with a particularly complex anatomy because of the frequency of wide-neck configurations with incorporating MCA branches. Endovascular treatment of MCA aneurysms can be technically more challenging, and in many institutions, surgical treatment is considered the first option because of the high rate of long-term occlusion with low surgical morbidity.⁴ However, with the improvement of angiographic images, increased operator experience, and the use of more complex techniques, an increasing number of MCA aneurysms are treated with endovascular techniques.¹ Recently, flow diversion has been used as an alternative technique for complex wide-neck MCA aneurysms, incorporating ≥1 side branch or in cases of previous endovascular or surgical failure.^5–14 However, the role of flow diversion in this location is controversial, and the efficacy and safety of this technique remain unclear. We performed a systematic review and meta-analysis of all published series examining flow diversions for the treatment of MCA aneurysms with the aim of clarifying the following: 1) aneurysm occlusion rate, 2) treatment-related complications and clinical outcome, and 3) the fate of the MCA side branch covered with the device.