Teaching Case

A 58-year-old man presented with hemoptysis with a right-sided paratracheal mass located in upper mediastinum in his chest roentgenogram.

A 58-year-old man presented with hemoptysis was hospitalized because of a mass detected on his chest roentgenograms. His history, physical examination and routine laboratory tests were unremarkable. A postero-anterior chest roentgenogram showed a right-sided paratracheal mass located in upper mediastinum. It was behind the medial end of right clavicle extending from the aortic knuckle. The medial margin of the lesion is silhouetting with the superior vena cava while the smooth lateral margin extends above the medial end of the clavicle. First a spiral chest CT examination and then an MRI examination was performed with a 1.5 Tesla superconducting magnet. Axial, coronal and sagittal electrocardiographically gated T1 and T2-weighted spin echo images and MR angiography of the aortic arch were obtained.

Aberrant right subclavian artery in the presence of an otherwise normal aorta is the most common anomaly of the aortic arch development, occuring in approximately 0.5 % of the population. It may arise directly from the arc of aorta as the first, second, third, fourth or even the fifth branch of that vessel. When it arises as the last branch in the left aortic arc, it courses behind the trachea or both the trachea and esophagus to reach the groove on the first rib. Since compression of the esophagus by the right subclavian artery into the aortic arc may cause dysphagia, the term dysphagia lusoria has been used to describe the symptom complex. Aneurysms that arise within the aberrant right subclavian artery occur most often in elderly patients and appear to be atherosclerotic in origin, but can also be affected by arteritis. It is commonly dilated at its origin. The presence of an aneurysm of the artery of Kommerell’s diverticulum at its aortic origin is a rare finding and more likely to produce symptoms. Bicarotid trunk variant is a frequent association with aberrant right subclavian artery. The aortic arch, higher than normal with a more directly anteroposterior orientation, is visible, as is the aberrant right subclavian artery arsing from the medial wall of the posterior portion of the arch or from the beginning of the descending aorta. With regard to the differential diagnosis, masses in the upper mediastinum such as lymphoma, bronchogenic carcinoma, thyroid carcinoma or goitre, esophageal carcinoma and lymphadenopathies of various origin could easily be excluded because of the vascular nature of the lesion. Chest radiography and barium esophagography are not spesific for the diagnosis of aneurysm of aberrant right subclavian artery. Chest CT proves complementary to these studies by clearly showing total vessel size, mural thrombus and anatomic relations to the adjacent mediastinal structures. However digital substraction angiography is necessary to plan the surgical intervention. As compared to these modalities, conventional MR imaging with MR angiography has been shown to be the best noninvasive method for diagnosing the aneurysm of aberrant right subclavian artery.