UPmémoires

English

Impact of the Global Outflow Angle on recanalization after endovascular treatment of Middle Cerebral Artery bifurcation aneurysms

Background and purpose: Intracranial aneurysm recanalization (IAR) after endovascular treatment (EVT) remains a major problem. As hemodynamic factors appear to play a key role in aneurysm formation, the same factors could lead to recanalization. The main goal of this study was to find new predictive factors of recanalization after EVT, by calculating 3D angle values between the arteries of the Middle Cerebral Artery (MCA) bifurcation, and in particular the Global Outflow Angle.

Materials and methods: Ninety-six aneurysms of MCA bifurcation, ruptured or not, treated only by endovascular approach between Septembre 2009 and December 2014 were included. Clinical factors, aneurysm size (height and width), height/width (H/W) ratio, neck size, postoperative occlusion class, percentage of packing volume and morphological parameters obtained from 3D angiography analysis (Inflow Angle, Outflow Angle 1 and 2, Global Outflow Angle) were studied. Angles were measured in 3D reconstructions of initial digital subtraction angiography (DSA), using three-dimensional coordinates of key points placed on parent and daughter arteries of MCA bifurcations. The Global Outflow Angle was the sum of the two lateral angles formed by parent M1 artery and each daughter M2 artery. Univariate and multivariate analyses were done.

Results: Recanalization occurred in 25 cases (26%) of all aneurysms included, and retreatment performed in 11 cases (11%). Only one patient (1%) had a rebleeding. Univariate analysis established as predictive factors of recanalization: high blood pressure (p=0.014), the aneurysm height (p<0.001) and width (p<0.001), neck size (p<0.001), postoperative occlusion class (p=0.040), percentage of packing volume (p<0.001), as well as the two Outflow Angles (p=0.006 and 0.045), and the Global Outflow Angle (p<0.001). Multivariate analysis established two independent risk factors of recanalization: the Global Outflow Angle (OR=1.05; 95% CI, 1.02-1.08; p<0.002) and the aneurysm width (OR=0.67; 95% CI, 0.46-0.96; p=0.031). A Global Outflow Angle threshold <192° was found to be a risk factor of recanalization (OR=13.75; 95% CI, 4.46-42.44) with a sensibility of 80% and a specificity of 77%. Inter- and intra-observer reproducibility of calculating 3D angle values were good.

Conclusion: This study emphasizes that a new parameter, the Global Outflow Angle, could be predictive of recanalization for MCA bifurcation aneurysms treated by EVT. This should be kept in mind during the periprocedural management of this subgroup of patients with a low Global Outflow Angle, and during their follow-up.