Unilateral enlargement of the foramen transversarium in the axis (C2) of an asymptomatic patient during routine dental iCAT scan

The foramen transversarium is an opening in the transverse process located in all seven cervical vertebra. It allows for the passage of the vertebral vessels and a plexus of sympathetic nerve fibers which normally enter the foramen transversarium at the sixth cervical vertebra (C6) as it passes towards the skull. The vertebral artery is a branch of the first part of the subclavian artery, which branches from the subclavian medial to the scalenus anterior muscle. Upon entering the foramen transversarium of C6, the vertebral artery will ascend in the foramen transversarium of the rest of the cervical vertebra to the base of the skull before passing medially through the foramen magnum to unite with the opposite vertebral artery forming the basilar artery. Various studies have shown that a small vertebral artery can be located on angiography when a small foramen transversarium is present. We report an unusually large left foramen transversarium on the axis (C2) in an asymptomatic patient that was being evaluated for dental work during a routine dental iCAT scan. The maximum diameter of the foramen was 1.8 cm. The foramen transversarium on the opposite side of the axis was normal. There was no other anomalous foramen transversarium associated with the remainder of the cervical vertebra on the patient.