Case Report A Case of Multiple Posterior Intercostal Artery Common Trunks in Conjunction with Additional Arterial Variations Nicholas R. Fanselow , Nolan Wallace , Daniel Sehi , Lokesh Coomar , John Martin , Yun Tan , and Daniel T. Daly Center for Anatomical Science and Education, Department of Surgery, Saint Louis University School of Medicine, Saint Louis, MO 63104, USA Correspondence should be addressed to Daniel T. Daly; daniel.daly@health.slu.edu Received 11 August 2021; Accepted 26 October 2021; Published 18 November 2021 Academic Editor: Christophoros Foroulis Copyright © 2021 Nicholas R. Fanselow et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Several thoracic vasculature variations were observed in an 81-year-old male cadaver during routine dissection. These included 5 common trunks of posterior intercostal arteries, a descending branch of the right vertebral artery, and atypical neurovascular relationships within intercostal spaces. On the right side, two common trunks of posterior intercostal arteries were observed supplying the 4th-7th intercostal spaces and 9th-11th intercostal spaces, respectively. There was also a small accessary branch supplying the 9th intercostal space. The first three posterior intercostal spaces on the right were supplied by a descending branch of the vertebral artery. On the left side, three common trunks of posterior intercostal arteries were encountered, supplying intercostal spaces 3-5, 6-7, and 11 plus the subcostal space. An atypical neurovascular relationship was observed in the right 6th intercostal space, as well as the left 2nd, 3rd, and 6th intercostal spaces. This is the first case report that presents 5 common trunks of posterior intercostal arteries, as well as common trunks in conjunction with other arterial variation in the posterior thoracic wall. These variations carry a high level of clinical significance and may be helpful in guiding decision- making related to surgical procedures related to the posterior thoracic cavity and spine. 1. Introduction The principal arterial supply of the posterior thoracic wall typically comes from 11 pairs of posterior intercostal arter- ies (PIAs) and one pair of subcostal arteries. The first two PIAs arise from the highest intercostal artery, a branch of the costocervical trunk [1]. PIAs 3-11 and the subcostal artery arise directly from the thoracic aorta (TA), in a seg- mental pattern [2]. PIAs typically travel in the superior aspect of the corre- sponding intercostal space (ICS) near the inferior border of their respective rib. The origin of these arteries is slightly cau- dal to where the PIAs are situated in the ICS thus requiring the PIA to travel superiorly and laterally along the lateral aspect of the vertebral column before reaching the costal groove on the inferior border of the corresponding rib [3]. Occasionally, PIAs run dorsally between the neck of the rib and vertebral transverse process, through the costotransverse foramen [4]. The typical organization of the intercostal neurovascular structures within the ICS is intercostal vein, artery, and then nerve from superior to inferior [5–7]. As the PIA travels in the ICS, it divides into two major divisions, which in turn gives off minor branches to supply numerous structures. These branches supply structures such as intercostal, pectoral, serratus, and deep back muscles, as well as the spinal cord and associated nerve roots, mammary glands, and skin [8, 9]. The right bronchial artery, which supplies areas of the right lung, often originates from the 3rd PIA on the right side [10–12]. Although the pattern described above is that which is most observed (Figure 1), there is a great deal of variation in the arterial branching pattern within the area. The most frequent Hindawi Case Reports in Surgery Volume 2021, Article ID 7430752, 7 pages https://doi.org/10.1155/2021/7430752