Comparison of carotid and basilar bifurcation aneurysms versus non-T-angled bifurcations: the geometry is associated with the outcome

Patients with ruptured aneurysms of carotid bifurcation artery seem to suffer less often from cerebral vasospasm and early brain injury and have a better clinical outcome. Aim of our study was to identify differences in clinical course and outcome in aneurysms of terminus segments (carotid bifurcation artery and basilar tip) compared to aneurysms of other aneurysm locations except carotid bifurcation artery and basilar tip. Patients with SAH were entered into a prospectively collected database (1999 to June 2014). A total of 471 patients (‘T-shaped’ aneurysms n = 63, ‘non-T-shaped’ aneurysms n = 408) were selected. Outcome was assessed by modified Rankin Scale (mRS) 6 months after SAH. Mean age was 53.75 years. Statistically, analysis showed a significant better outcome in ‘T-shaped’ aneurysms (p = 0.0001) and a significant lower mortality rate (p = 0.02) despite higher rates of Fisher 3 bleeding pattern and CVS. In ‘T-shaped’ aneurysms, no prognostic factors for outcome could be detected. In ‘non-T-shaped’ aneurysms admission status (p < 0.0001), early hydrocephalus (p < 0.0001), shunt-dependence (p = 0.001), and the occurrence of severe CVS (p = 0.01) statistically were factors influencing patients’ outcome. Multivariate analysis showed ‘non-T-shaped’ aneurysms itself as independent prognostic factor for patients’ outcome. Despite same rate of poor admission status, early hydrocephalus and shunt dependence ‘T-shaped’ aneurysms have a highly significantly better. Pathophysiological mechanism actually is not understood. Further studies are necessary to identify, which factors lead to the decreased outcome in “non-T-shaped”- aneurysms.