PHOTO: EAST NEWS/PHANIE
Three-dimensional computed tomographic (CT) scan reconstruction of a skull showing an intracranial aneurysm (red ballon shaped swelling) located in the arterial circle of Willis (where the basilar artery and internal carotid arteries meet). An aneurysm is a bulge of a vessel due to the dilatation of its wall. A ruptured aneurysm can be fatal.