Anatomic variations in origin and coursing of the transverse cervical artery: morphogenesis and relation to the high arch-shaped subclavian artery

This case report presents an atypical transverse cervical artery with its detailed anatomy, morphogenesis, and association with the high arch-shaped subclavian artery. The atypical arteries, related arteries, and adjacent cervical and brachial plexuses were macroscopically examined in a 98-year-old Japanese female cadaver donated to The Nippon Dental University for medical education and research. The atypical deep branch of the transverse cervical artery originated from the internal thoracic artery and passed through between the C5 and C6 roots, in close contact with the C5 and C6 junction, to reach the dorsal side of the brachial plexus. The right subclavian artery exhibited a high arch-shaped coursing and traveled approximately 18 mm higher than the left subclavian artery. This atypical transverse cervical artery exhibits a combination of rare variations in its origin and course. The previous reports revealed that the transverse cervical artery arising from the proximal part of the subclavian artery tends to pass the lower part of the brachial plexus. However, this does not apply to the present case, implying that this atypical artery develops in a different manner from those previously described. Furthermore, the high arch-shaped subclavian artery in this case presumably arose by the suspension of the atypical transverse cervical artery at the C5 and C6 roots junction in a pulley-like structure. Clinicians performing pre- and intraoperative evaluations of neck surgery and catheterization of related arteries should consider that congenital anatomic variations in the transverse cervical artery may have cause anomalous subclavian artery coursing.