Thoracic aortic aneurysms are caused by hardening of the arteries (atherosclerosis), high blood pressure (hypertension), congenital disorders such as Marfan's syndrome, trauma, or less commonly, syphilis.

Atherosclerosis is by far the most common cause.

Thoracic aneurysms occur in the ascending aorta (25% of the time), the aortic arch (25% of the time), or the descending thoracic aorta (50% of the time).

Risk factors include various connective tissue disorders (such as Marfan's syndrome), atherosclerosis, previous dissection of the aorta, prolonged hypertension, and trauma (usually falls or motor vechicle accidents).

Most patients have no symptoms until the aneurysm begins to leak or expand. Most non-leaking thoracic aortic aneurysms are detected by tests -- usually a chest X-ray or a chest CT scan -- run for other reasons. Chest or back pain may indicate acute expansion or leakage of the aneurysm.

The physical examination is often normal. A chest X-ray and chest CT scan demonstrate enlargement of the aorta. A chest CT scan identifies the diameter of the aorta and the exact location of the aneurysm.

An aortogram (a special set of X-ray images made during injection of dye into the aorta) may also identify the location and extent of the aneurysm and identify any branch arteries of the aorta that are also involved.

The treatment depends on the location of the aneurysm.

For patients with aneurysms of the ascending aorta or aortic arch, surgery to replace the aorta is recommended if the diameter of the aorta measures greater than 5-6 cm. The aorta is replaced with a fabric substitute in an operation that uses a heart-lung machine. If the aortic arch is involved, a specialized technique called "circulatory arrest" -- a period without blood circulation while on life support -- may be necessary.

For patients with aneurysms of the descending thoracic aorta, two options are available. For patients with aneurysms that are larger than 6 cm, an operation for replacement of the aorta with a fabric substitute can be done, or the aorta can be stented.

Stenting involves the use of a tube placed inside the vessel and can be performed without a chest incision, with specialized catheters that are introduced through arteries at the groin. Not all patients with descending thoracic aneurysms are candidates for stenting, however.

The long-term prognosis for patients with thoracic aortic aneurysm is determined by other medical problems such as heart disease and diabetes, which may have caused or contributed to the condition.

Serious complications after aortic surgery can include: heart attack, irregular heartbeats, bleeding, stroke, paralysis, graft infection, and kidney damage. Death soon after the operation occurs in 5-10% of patients.

Patients with chest or back discomfort should consult their physician. Patients with a family history of connective tissue disorders should notify their physician.

Prevention measures for atherosclerosis, in general, include not smoking, controlling blood pressure and blood lipid levels, and exercising routinely.