Rare Bilateral Variation of the Posterior Intercostal Arteries

BackgroundThe thoracic aorta usually gives off the 3rd to 11th pairs of posterior intercostal arteries (PIA) and 1 pair of subcostal arteries. The first two pairs of PIA typically originate via the highest intercostal artery via the costocervical trunk of the subclavian artery. The PIA supply blood to the intercostal spaces, spinal cord and spinal nerve roots.A bilateral branching anomaly in multiple PIA were observed in an 81 year‐old male cadaver during routine dissection. The thoracic aorta gave rise to asymmetrical common PIA trunks at different levels on both sides. Five common PIA trunks were found arising from the thoracic aorta and a descending branch of the right vertebral artery was also observed. Two common PIA trunks were observed on the right side branching from the thoracic aorta. The first common PIA trunk supplied the 4th through 7th intercostal spaces while the second common PIA supplied the 10th and 11th intercostal spaces. The 8th and 9th PIAs were direct branches off the thoracic aorta as normal. Three common PIA trunks were observed on the left side originating from the thoracic aorta. The first common trunk supplied the 3rd through 5th intercostal spaces. The second supplied the 6th and 7th intercostal spaces. The third trunk was observed to supply the 11th intercostal space as well as the subcostal region. Another vascular variation observed included a branch from the right vertebral artery that descended inferiorly and dorsally toward the first four ribs through the right costotransverse foramen. This descending branch of the vertebral artery gave off branches to supply the second, third, and fourth intercostal spaces on the right side. While common trunks of PIA have been reported to be highly prevalent, there are normally 1–2 common trunks found in a typical thorax. Thus, a cadaver that displays up to 5 common trunks of PIA in a singular thorax is a rare occurrence. Also anomalous is the presentation of a direct branch of the vertebral artery that courses dorsal to ribs while supplying several intercostal spaces. Understanding such anomalies has important clinical implications to interventional radiologists during thoracic cavity procedures as well as spine and thoracic surgeries.Support or Funding InformationCenter for Anatomical Science and Education, Department of Surgery, Saint Louis University School of MedicineThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.