Flow-Diverting Stents for Intracranial Bifurcation Aneurysm Treatment

BACKGROUND: Although initially considered safe when covering bifurcation sites, flow-diverting stents may provoke thrombosis of side branches that are covered during aneurysm treatment. OBJECTIVE: To understand the occurrence and clinical expression of side-branch remodeling in distal intracranial arterial sites after flow diverter deployment by means of correlation of imaging and clinical data. METHODS: We analyzed our prospectively collected data on a series of patients treated with flow diverters for intracranial aneurysms at bifurcation sites. From February 2011 to May 2013, 32 patients with 37 aneurysms (anterior communicating artery, 9 [24.3%]; anterior cerebral artery, 5 [13.5%]; middle cerebral artery, 19 (51.4%); terminal internal carotid artery, 4 [10.8%]) were treated. We divided aneurysms into 2 groups based on the side branches covered by the stent during treatment. Group A consisted of cases with side branches that supplied brain territories also receiving a direct collateral supply. Group B consisted of cases in which side branches supplied territories without direct collateral supply. The 2 groups were compared statistically. RESULTS: Total exclusion occurred in 97.3% of aneurysms at follow-up. Initial modified Rankin Scale (mRS) score was 0 to 1 for 29 patients (90.6%) and 2 for 3 patients (9.4%). New permanent neurological deficit was reported in 3 patients (9.4%). At the 6-month follow-up, the mRS score was 0 to 1 for 31 patients (96.8%) and 3 for 1 patient (3.2%). Although 78.5% of side branches in group A underwent narrowing or occlusion after 6 months, no new stroke was found on magnetic resonance imaging. CONCLUSION: Symptomatic modifications of side branches after flow diverter treatment depend on the extent and type of collateral supply.