Variations of transverse foramina in cervical vertebrae: what happens to the vertebral artery?

The purpose of this study is to examine variations of the foramen transversarium and the vertebral artery in computed tomography angiographies (CTa) of the cervical spine, investigate their coexistence, and present possible considerations regarding such variations in spine surgical procedures.

Fifty CTa of the neck were retrospectively reviewed. Transverse and anteroposterior diameter of the foramen and diameter of the vertebral artery were measured. Variations of the foramen and the vertebral artery were detected.

Cervical CTa of 32 males and 18 females (mean age 66.4 ± 10.78 years), all belonging to the Indo-European race, were reviewed. Variations of the foramen transversarium were found in 17 vertebrae (4.85%) of 15 patients (30%). Duplication of the foramen was the most frequent variation, followed by the open foramen, the absence of the foramen, the triple foramen, and the hypoplastic foramen. Variations of the vertebral artery were found in 7 patients (14%) and asymmetry was found in 12 (24%) patients. Moreover, six patients presented with hypoplastic vertebral arteries (12%). When examining coexistence, 60% of patients exhibiting variations in the transverse foramen were also exhibiting variations or asymmetry in the vertebral artery, compared to 25.7% of patients with no foramen variations (p = 0.02).

Vertebral artery injury is not common but may be a disastrous complication during cervical spine surgery. Proper preoperative planning is essential for any surgeon and exact knowledge of the anatomy in each patient is essential. This study strongly recommends the preoperative use of a CTa when suspicion of a variation is present and implied by a foramen variation. These slides can be retrieved under Electronic Supplementary Material.