Aneurysms of the aorta in the chest are much less com¬mon than abdominal aneurysms. They are classified as the ascending, arch, or descending aortic aneurysms. Because of the etiology and natural history, treatment differs for each of these aortic segments. Aneurysms of the descend¬ing thoracic aorta are the most common and have similar causes as those of abdominal aneurysms. Aneurysms of the descending aorta usually result from a cystic medial necrosis; the etiology of which remains unknown. Also, cystic medial necrosis is observed in nearly all cases of Marfan syndrome. Another rare connective tissue disorder, Ehlers-Danlos syndrome, may involve the aorta. Syphilis was a common cause of ascending thoracic aneurysms, but is now rare because aggressive antibiotic therapy cures the disease in its early stages. In these cases chest x-ray showed typical linear calcification of the dilated ascending thoracic aorta.
A. Signs and Symptoms
More than 40% of patients are asymptomatic when first diagnosed mainly by routine chest radiography. A large ascending aortic aneurysm may compress the veins that return blood from the head and neck to the heart via the superior vena cava. The aneurysm of the aortic arch or descending aorta may compress the trachea and cause cough, shortness of breath, wheezing, and hemoptysis. Posterior compression of the esophagus may cause diffi¬culty in swallowing and compression of the recurrent laryngeal nerve may produce hoarseness. Pain in the back and chest may occur; this is usually a constant deep, boring pain that can sometimes be severe.

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