A cerebral aneurysm is a common cerebrovascular disorder caused by a weakness in the wall of an artery that supplies blood to the brain. This weakening results in an abnormal widening or ballooning of the artery, and increases the risk for a subarachnoid hemorrhage; a rupture or bursting of the aneurysm. The most common location for brain aneurysms is in the network of vessels at the base of the brain. The disorder may result from congenital defects, preexisting conditions such as high blood pressure, a history of smoking, a family history of brain aneurysms, or from head trauma. Brain aneurysms occur more commonly in adults than in children and are slightly more common in women than in men, however they may occur at any age.