| Summary: | Objective: Various risk factors for recanalization after coil embolization have been reported, but the indications for retreatment of recanalized aneurysms have not been determined.The aim of this study was to identify risk factors indicating the need for retreating recanalization during long-term follow-up (approximately 1 year). Methods: A total of 172 unruptured saccular aneurysms in 155 patients treated by initial coil embolization between February 2012 and July 2019 were retrospectively analyzed. Intraluminal thrombosed aneurysms, aneurysms treated with stent assistance, and aneurysms followed without digital subtraction angiography (DSA) were excluded. Recanalization was identified in 31 aneurysms. Recanalized aneurysms (Meyer grade ≥2) were defined as major recanalization (MA); those that worsened to Meyer grade 1 were defined as minor recanalization (MI). Age, sex, aneurysm location, shape, five morphological variables (neck, height, width, dome-to-neck ratio, aspect ratio), aneurysm volume, endovascular technique, immediate Meyer grade, and volume embolization ratio (VER) were compared between MI (n = 18) and MA (n = 13). Predictors of MA were determined using logistic regression and receiver operating characteristic (ROC) curve analyses. Results: On multivariate logistic regression analysis, spherical shape (odds ratio (OR) 11.9; 95% confidence interval (CI) 1.28–111) and VER (OR 1.92; 95% CI 1.13–3.28) were independent predictors of MA. On ROC curve analysis, the optimal cut-off value for the VER was 20.8% (sensitivity, 76.9%; specificity, 77.8%). Conclusions: Lower VER and non-spherical shape appear to be independent risk factors for progression to MA in recanalized aneurysms, and packing with a VER >20.8% is expected to prevent progression to MA.
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