Meta-analysis of Treatment Outcomes of Non-saccular Aneurysms in the Posterior Circulation by Flow Diverters

Background Non-saccular aneurysms of the posterior circulation are uncommon but highly dangerous lesions. Flow diverter stents have been demonstrated to be effective treatments of various anterior circulation aneurysms, particularly large and giant proximal internal carotid artery aneurysms. However, evidence regarding the treatment of non-saccular posterior circulation aneurysms with flow diverters is lacking.

Methods A systematic literature review of the English language literature since 2007 was conducted using PubMed, MEDLINE, and Embase. Keywords and MeSH terms included flow diversion, flow diverter, pipeline, surpass, intracranial aneurysm, vertebrobasilar, non-saccular. Case reports were excluded. Angiographic and clinical outcomes were pooled using a random-effects meta-analysis.

Results Thirteen retrospective noncomparative studies reporting 129 patients and 131 aneurysm treatments were included. The average number of flow diverters per aneurysm was 4.33. Immediate complete or near-complete occlusion of the aneurysm occurred in 25% (95% CI: 1–60%), and long-term occlusion in 52% (29–76%). Periprocedural stroke occurred in 23% of cases. Good long-term neurologic outcome (modified Rankin's scale ≤2) was achieved in 51% (95% CI: 31–71%). Overall mortality was 21% (95% CI: 7–38%), and morbidity was 26% (95% CI: 12–42%). Retreatment was required in 5% (95% CI: 0–14%). Good neurologic outcome rate was higher in vertebral artery aneurysms (83%) than other locations (18–33%).

Conclusion Flow diversion is a feasible and efficacious treatment of non-saccular aneurysms in the posterior circulation. However, the intervention carries a significant risk of periprocedural stroke, and is still associated with high overall mortality. Further studies are needed to identify significant treatment risk factors and optimize patient selection.