Cerebral aneurysms are bulges on the artery and are most commonly located at bifurcations in the vicinity of the Circle of Willis. The presence of aneurysms are statistically linked with morphological features of the main arteries supplying the brain with blood. Previous work by Bergersen (2016) studied wider angles in the terminus bifurcation of the internal carotid artery (ICA), and area variations of the vessel. The goal of this thesis was to continue development of methods used to manipulate morphological features in the ICA. We explored angle and curvature variations in the carotid siphon bend located in the ICA, upstream of where most aneurysms are formed. The manipulations were performed on ten healthy patient-specic models. We studied hemodynamic stimuli at the bifurcations and the presence of turbulent ow. Curvature variations were found not to aect the time-averaged wall shear stress. However, the occurrence of unstable ow varied slightly, without following any particular trend. Similarly, angle variations were found not to aect the hemodynamic stress, but correlated with the presence of unstable ow. The results are in contradiction to the leading theory for aneurysm initiation, and suggest that the temporally varying stress from the unstable ow is a plausible source for aneurysm initiation.