Subtle or atypical injuries of the thoracic aorta and brachiocephalic vessels in blunt thoracic trauma.

Aortic or brachiocephalic vessel injuries secondary to blunt thoracic trauma are relatively common and can occur throughout the length of the thoracic aorta or in various locations in the brachiocephalic vessels. Aortography remains the standard of reference for the diagnosis of these injuries despite recent technologic advances in other imaging modalities. The classic aortographic finding in aortic or brachiocephalic vessel injury consists of a large false aneurysm, typically protruding from the medial aspect of the aortic isthmus. However, intrathoracic aortic or brachiocephalic vessel injury can and does occur at any intrathoracic location and may exhibit a wide variety of radiographic appearances, thereby presenting a diagnostic challenge even for experienced trauma angiographers. Large false aneurysms may appear oval or rounded, tubular, or asymmetrically globular and may manifest in unusual locations such as the ascending aorta. Although smaller, irregularly shaped false aneurysms at atypical locations may be obscure or mimic ductus diverticula, their irregular, sharp margins allow them to be distinguished as injuries. The subtlety of aortic or brachiocephalic vessel injuries necessitates a high degree of suspicion along with meticulous imaging technique in all cases and the use of additional projections in equivocal cases for definitive diagnosis.