Effects of anatomic characteristics of aneurysms on packing density in endovascular coil embolization: analysis of a single center’s experience

When embolizing cerebral aneurysms, dense coil packing may prevent recanalization but this may be influenced by the aneurysm morphology. We have analyzed retrospectively the relationship between anatomic features and the volumetric coil packing density. We analyzed 452 aneurysms in 434 patients treated by coil embolization without stenting, expressing packing density as volume embolization ratio (VER, volume of inserted coils/aneurysm volume). Six morphological variables (neck width, height, maximum diameter, dome to neck ratio (DNR), and aspect ratio), aneurysm location, and whether the aneurysm was ruptured or unruptured were analyzed with respect to dense (VER ≥20 %) or loose (VER <20 %) packing densities, using logistic regression analysis and ROC analysis. Among 452 aneurysms, VERs >20 % were achieved for 272 aneurysms, with a mean VER of 24.7 %. The mean VER of the remaining 180 aneurysms was 15.6 %. In univariate analyses, the predictors for dense packing were having an anterior circulation, DNR, aspect ratio, and neck width. In multivariate analysis, the independent predictors were smaller neck width (odds ratio (OR) 0.8735; 95 % confidence interval (CI) 0.7635–0.9993) and larger aspect ratio (OR 1.6679; 95 % CI 1.0460–2.6594). ROC analysis showed optimal cutoff values for an aspect ratio of 1.35 (sensitivity 69.5 %, specificity 51.7 %) and a neck width of 3.13 mm (sensitivity 51.1 %, specificity 27.8 %). Although dense coil packing is still difficult to achieve in wide-necked aneurysms without the use of stents, packing with VER >20 % is expected to be achieved when the height is 1.35 times larger than the neck width.