This bulge or weakening usually occurs on larger blood vessels where an artery branches. Fusiform - when the wall bulges in all directions and has no distinct neck. Mycotic - caused by a bacterial infection of the arterial wall and is relatively rare. Traumatic - occur as a result of a closed head injury or penetrating trauma to the brain. It is rare for an aneurysm to occur in the very young or the very old.
Most aneurysms result from the development of abnormal arterial vessel walls.
They also can result from trauma or infection, but this is very rare. The highest incidence of brain aneurysms occurs in the 40 to 60 age group. Aneurysms can enlarge and cause pressure on surrounding structures, causing headache or visual disturbances, and may eventually rupture. The rupturing of an aneurysm causes a subarachnoid hemorrhage, which is a very life threatening situation. Rupture usually occurs while a person is active rather than asleep.