An aneurysm is a localized sac or dilation formed at a weak point in the wall of the aorta. Aneurysms can enlarge and produce complications by compressing surrounding structures. There are different types of aneurysms including saccular, fusiform, and berry aneurysms which vary in shape and size. Common causes of aneurysms include atherosclerosis, infections, trauma, and hereditary conditions like Marfan syndrome. Symptoms depend on the location but may include chest pain, shortness of breath, and pulse abnormalities. Diagnosis is often by imaging tests and treatment depends on the size and type but may include surgery to repair or replace the damaged vessel.