Ponticulus posticus occurs due to calcification of the oblique atlanto-occipital ligaments and is known by many names such as Kimerle foramen,  foramen arcuale atlantis or arcuate foramen.

The ponticulus posticus means "little posterior bridge" in Latin It was defined as an abnormal small bony bridge formed between the posterior portion of the superior articular process and the posterolateral portion of the superior margin of the posterior arch of the atlas

The sulcus situated on the posterolateral margin of the atlas forms a groove for the vertebral artery. The vertebral artery (atlantic portion V3 )  passes through this foramen.

It has a variable morphology, can be complete or incomplete and may be unilateral or bilateral.

More common in females.