Aneurysms form at branching points in the arteries where there is continual pressure from flowing blood; generally they become weaker as they grow, according to the American Stroke Association. Aneurysms are closely associated with cerebral arteritis, arterial dissection and fibromuscular dysplasia, which are all blood vessel disorders, and some people may be genetically predisposed to them. Aneurysms may also occur due to an infection, as a result of drug abuse that damages the blood vessels in the brain or from trauma incurred during an injury.
Usually, people develop aneurysms at age 40 or older; they are seldom born with them. Typically, aneurysms are located in the major arteries deep with the structures of the brain. They can occur in both the back and front parts of the brain and are generally diagnosed with CT scans and other special imaging tests.
Small aneurysms rarely present symptoms, but as an aneurysm grows, it may cause localized pain and headaches. If it becomes very big, it can press on brain tissue and cause weakness in the legs or arms, seizures, memory problems and vision problems. If an aneurysm ruptures, it can cause severe headaches that can last for hours or days, vomiting, nausea, drowsiness or coma. The risk of moderate to severe brain damage is 20 to 35 percent once an aneurysm bleeds, with a 30 to 40 percent chance of death.