Click Image to Enlarge. A cerebral aneurysm (also called an intracranial aneurysm or brain aneurysm) is a bulging, weakened area in the wall of an artery in the brain, resulting in an abnormal widening, ballooning, or bleb.Because there is a weakened spot in the aneurysm wall, there is a risk for rupture (bursting) of the aneurysm. normal artery wall is made up of three layers. The aneurysm wall is thin and weak because of an abnormal loss or absence of the muscular layer of the artery wall, leaving only two layers. The most common type of cerebral aneurysm is called a saccular, or berry, aneurysm, occurring in 90 percent of cerebral aneurysms.