A cerebral aneurysm is the dilation, bulging or ballooning out of part of the wall of a vein or artery in the brain. The disorder may result from congenital defects or from other conditions such as high blood pressure, atherosclerosis (the build-up of fatty deposits in the arteries), or head trauma. Cerebral aneurysms can occur at any age, although they are more common in adults than in children and are slightly more common in women than in men. The signs and symptoms of an unruptured cerebral aneurysm will partly depend on its size and rate of growth