Flow Diversion in Middle Cerebral Artery Aneurysms: Is It Really an All-Purpose Treatment?

BACKGROUND AND OBJECTIVE: The outcome of flow diversion for middle cerebral artery (MCA) aneurysms, one of the most common sites for intracranial aneurysms, has not been defined thoroughly. We assessed our outcomes in MCA aneurysms (MCAAs) treated by flow diversion, i.e., with either dedicated flow diverters or telescopic stents. METHODS: Patients with MCAAs were treated by flow diversion if surgical or other endovascular treatment modalities had failed or were deemed likely to fail. Angiographic and clinical outcome of these patients was assessed retrospectively. Aneurysm location on MCA was defined as M1 segment, "true bifurcation" (classical bifurcation of MCA into superior and inferior trunks), "variant bifurcation" (bifurcation of early frontal or early/distal temporal branches), or M2 segment. Aneurysm morphology was classified as saccular versus dissecting/fusiform. RESULTS: Treatment was attempted in 29 MCAAs. Technical failure rate was 3.4% (1/29). Thirteen of aneurysms were fusiform. Of the bifurcation aneurysms, most (10/16) were the variant type. Overall and procedure-related mortality/permanent morbidity rates were 10.3% (3/29) and 3.5% (1/29). Total occlusion rates (mean angiographic follow-up 10.3 months) for saccular and fusiform aneurysms were 40% and 75%, respectively. In bifurcation aneurysms, occlusion was strongly associated with sidebranch occlusion (P < 0.005). CONCLUSIONS: In this series, flow diversion for the treatment of MCAAs was safe, was effective in the treatment of fusiform MCAAs, and was not as effective at midterm for MCA bifurcation aneurysms. Unsatisfactory occlusion rate in bifurcation aneurysms likely results from residual filling of the aneurysms in cases in which the jailed side branch remains patent.