Morphometric predictors of posterior circulation aneurysms risk rupture.

Objectives: Intracranial aneurysms (IAs) of the posterior circulation (PC) rupture more frequently and their morbidity and mortality rates are higher compared to anterior circulation. Morphological parameters such as size ratio (SR), inflow angle and parent artery geometry are believed to contribute significantly in determining IA risk rupture. The aim of this study is to establish angiography-based morphometric predictors of PC IA risk rupture.

Methods: A retrospective analysis of 58 patients with PC aneurysms was incorporated into the study. The following independent variables were measured: aneurysm dome size, neck size, parent artery size, SR, neck to parent artery ratio, and inflow angle. All aneurysms were divided into ruptured and unruptured groups. The stepwise logistic regression analysis was applied to establish the predictors of PC aneurysm risk rupture.

Results: 58 patients with 27 unruptured and 31 ruptured PC cerebral aneurysms were analyzed. The mean aneurysm dome, neck and parent vessel diameters were 8·49±3·5 mm, 2·46±1·4 mm, and 3·92±1·6 mm, respectively. Size ratio was 2·26±0·6; dome/neck 3·45±0·8 and inflow angle 115·2±22°. The relevant difference between unruptured and ruptured groups was: SR (1·91 vs 2·48), aneurysm dome (7·96 vs 8·95 mm), dome/neck (3·77 vs 3·18), and inflow angle (103·7 vs 125·2°). The significant predictive value was reached for inflow angle (OR 1·05; Cl 95% 1·01 to 1·1) and SR (OR 3·53; Cl 95% 1·09 to 11·5). Cut-off value on receiver operating characteristic curve for inflow angle (113·1°; sensitivity 67·7% and specificity 81·5%) and SR (1·99; sensitivity 77·4% and specificity 63%).

Discussion: The SR and inflow angle proved to be relevant predictors in estimating the aneurysm risk rupture of the posterior cerebral circulation.