Accessory transverse foramina in the cervical spine: Incidence, embryological basis, morphology and surgical importance

Aim: To study the incidence of accessory foramina transversaria in cervical spine and to analyze them morphologically with emphasize on their embryological and surgical importance. Material and Methods: The study included 363 human cervical vertebrae which were procured from the bone collections of the Department of Anatomy. The foramen transversarium was observed macroscopically on both sides of all the vertebras, the accessory foramina were noted. Results: Out of 363 specimens, only 6 (1.6%) vertebrae showed the accessory foramina. Among them 5 (1.4%) vertebra had double foramina and only 1 (0.3%) vertebra showed three foramina. Only 1 (0.3%) vertebrae showed the foramen on both sides and the remaining 5 (1.4%) had unilateral foramina. Among the unilateral, 4 were present on the right side and only 1 was on the left side. No vertebrae showed the absence of foramen transversarium. Conclusion: The present study observed the accessory foramina transversarium in 1.6% of cases. The unilateral presence was more common than the bilateral. The surgical anatomy of these variations is important for the neurosurgeons and radiologists for interpreting the computed tomogram and magnetic resonance image scans. Their morphological knowledge is clinically important since the course of the vertebral artery may be distorted in such situations.