Use of Flow Diversion for the Treatment of Distal Circulation Aneurysms: A Multicohort Study

The safety and efficacy of flow diversion for distal circulation aneurysms of the cerebral vasculature has not been well evaluated. The objective of this study was to assess the use of flow diversion for distal circulation aneurysms (defined as at or beyond the M1, P1, and A1 segments of the middle cerebral artery, posterior cerebral artery, and anterior cerebral artery, respectively) in an international multicenter cohort. Clinical and radiologic records from all patients undergoing flow diversion treatment of distal circulation aneurysms at 3 academic centers (2 in the USA and 1 in Europe) from 2014 until 2017 were retrospectively reviewed. Forty-six patients (mean age, 58.2 years; 33 women) harboring 46 aneurysms who underwent treatment with either the Pipeline Embolization Device (Medtronic Inc., Dublin, Ireland) or the Flow Re-Direction Endoluminal Device (MicroVention, Tustin, California, USA) were included in these analyses. Thirty-four aneurysms (74%) were located in the anterior circulation and 12 (26%) were located in the posterior circulation. With a mean follow-up of 13.0 months, complete (100%) and near-complete (90%–99%) occlusion was noted in 36 aneurysms (78.2%). Angiographic evidence of side branch or perforator vessel coverage was present in 35 aneurysms (76.1%) but was not associated with failure to occlude at follow-up (P = 0.06). All patients had good functional outcomes after treatment (modified Rankin Scale score 0–2). There were 2 cases (4.3%) of perforator vessel stroke and no hemorrhagic complications. Flow diversion for aneurysms beyond the circle of Willis has occlusion rates comparable to alternative treatments and low morbidity. The clinical significance of flow limitation through covered side branches requires further investigation.