Incidence of the Arcuate Foramen of Atlas Vertebra and its Morphometric Differences with the Ipsilateral Transverse Foramen in the Egyptian Population

Document Type : Original Article


The Department of Anatomy, Faculty of Medicine, Sohag University


Abstract Background: The first cervical (atlas) vertebra has no vertebral body and consists only of 2 lateral masses (right and left) interconnected by the anterior and posterior arches. The third part of the vertebral artery (VA) passes inthe retroarticular groove on the upper surface of the posterior arch of atlas just behind the lateral mass. A bony bridge called ponticulus posticus (Posterior ponticle) may form over the retroarticular groove transforming it into a retroarticular canal (Arcuate foramen) that occasionally compresses the vertebral artery leading to disturbed blood supply of the posterior part of the brain. Aim of Study: This study was performed for assessment of the incidence of the arcuate foramen (AF) of the atlas vertebra in the Egyptian population and to compare its dimen-sions with the ipsilateral transverse foramen of atlas to evaluate the role of the arcuate foramen as an occasional cause of the VA compression. Material and Methods: The atlas vertebrae in the Anatomy departments, Faculties of Medicine of Cairo, Ain Shams, Al-Azhar, Helwan, Benha, Suez Canal, Zagazig, Tanta, Kafr El-Sheikh, Mansoura, Beni Suef, Minia, Fayoum, Assiut, Sohag and South Valley Universities were demonstrated for the presence of the AF. The dimensions of the arcuate foramina were measured by the Bacolis digital caliper and compared to the dimensions of the ipsilateral transverse foramina of atlas. Results: About 12.6% of the atlas vertebrae have AF. All arcuate foramina were narrower than the ipsilateral transverse foramina. Conclusion: About 12.6% of the Egyptian population have AF on the first cervical vertebrae. These foramina are narrower than the ipsilateral transverse foramina, so the presence of the AF represents a possible cause for compression of the VA.