Most ascending aortic aneurysms are caused by cystic degeneration of the middle layer of the aortic wall. Most patients are young or middle-aged, and often have enlarged aortic sinus and valve ring. In severe cases, the aortic valve leaflets cannot close together during diastole, resulting in aortic regurgitation. However, there are no obvious lesions in the aortic valve leaflets themselves. Some patients may have signs of Marfan syndrome such as long head, high arched upper jaw, slender trunk, limbs, and fingers, hyperextension of joints, pigeon chest or funnel chest deformity, and congenital dislocation of the lens. Other causes of ascending aortic aneurysms include atherosclerosis, syphilitic aortitis, and chest trauma.