A right aortic arch (RAA) is a rare vascular anomaly that often coexists with an aberrant left subclavian artery (ALSA). Due to the rarity of RAA, the development of an ALSA is not well understood.

We describe a case in which a 58-year-old man who was scheduled to undergo posterior decompression and fusion surgery for thoracic ossification of the posterior longitudinal ligament from Th1 to Th3 was found to have a RAA and an ALSA.

Preoperative computed tomography angiography demonstrated a RAA and an ALSA. The ALSA was extremely tortuous and ran in the paraspinal muscles behind the thoracic laminae, which meant it was in the surgical field. The ALSA arose from the descending aorta and bifurcated into the left segmental arteries of Th1 and Th2, and also bifurcated into the left vertebral artery, which had a normal subsequent course. The dysplastic ALSA was considered to have developed from the thoracic intersegmental artery. Based on preoperative examination findings, we performed spinal surgery without vessel injury.

We report a rare case of a dysplastic ALSA that developed from the thoracic intersegmental artery with a RAA. The knowledge of this anomaly provides safety in spinal surgery of the cervicothoracic junction.