Location and Course
The brachiocephalic trunk is located in the superior mediastinum. The superior mediastinum lies above the imaginary plane passing through the upper margin of the pulmonary roots.
It arises from the convex surface of the aortic arch (arcus aortae), being its first branch (from right to left). The origin of the trunk lies slightly to the left of the midline, after which the vessel, about 4 cm long, runs upward and to the right toward the right sternoclavicular joint, where it bifurcates into the right common carotid and right subclavian arteries. On the anterior thoracic wall, the trunk is projected over the area of the manubrium of the sternum.
Topography and Relations
The brachiocephalic trunk has close topographical relations with the organs and vessels of the mediastinum and neck:
- Anteriorly: The trunk is separated from the manubrium of the sternum by the left brachiocephalic vein (v. brachiocephalica sinistra), as well as the sternothyroid and sternohyoid muscles. To the right and anteriorly, it is partially covered by the mediastinal pleura.
- To the right: The right brachiocephalic vein runs along the right wall of the artery. Brachiocephalic lymph nodes (nodi lymphoidei brachiocephalici) are located in the region of the brachiocephalic veins.
Branches
At the level of the right sternoclavicular joint, the brachiocephalic trunk divides into the right common carotid and right subclavian arteries:
- Right common carotid artery (a. carotis communis dextra) — ascends in the neck without giving off branches until its bifurcation. It enters the carotid system.
- Right subclavian artery (a. subclavia dextra) — gives rise to the vertebral artery (a. vertebralis). The vertebral artery is a critical source of blood supply to the upper cervical segments of the spinal cord and contributes to the vertebrobasilar system.
Additional branch: Occasionally, the lowest thyroid artery (a. thyroidea ima) arises directly from the brachiocephalic trunk.
Anatomical Variants
The anatomy of the aortic arch branches is variable. The following variants are described for the brachiocephalic trunk:
- The trunk may be completely absent. In this case, the right common carotid and right subclavian arteries arise directly from the aortic arch.
- The trunk may originate from the left side of the aortic arch.
- In rare cases, two brachiocephalic trunks (right and left) are formed.
Clinical Significance
- Atherosclerosis: The brachiocephalic trunk is a common site for arterial stenosis and occlusion.
- Aortic surgery: During open surgical repair of aortic arch aneurysms under circulatory arrest, antegrade cerebral perfusion is recommended. The brachiocephalic trunk is one of the preferred access sites for arterial cannulation, often utilizing an additional synthetic vascular graft.