Rare association of anatomical variations of the atlas and the occipital in a case with cranial deformation.

The paracondylar process is an exostosis, situated lateral to the occipital condyles, which expands towards the transverse process of the atlas. The epitransverse process of the atlas is a bony outgrowth that extends from the transverse process towards the occiput. Ponticulus posterior is a bony bridge that spans from the lateral mass of the atlas towards the posterior extremity of the vertebral artery groove. They are important anatomical variations. In this article, we analyze a rare situation of concomitant presence of ponticulus posterior, foramen arcuate, paracondylar process and epitransverse process, all of them situated on the right side of an individual with artificial cranial deformation from the fifth century AD. The paracondylar process and the epitransverse process form an accessory atlantooccipital joint. The expression of these variations, though under genetic influence, might have also been influenced by artificial cranial deformation. To our knowledge, this association has not been reported. The epitransverse process and the ponticulus posterior are important because of the positional relationship with the vertebral artery on which they may exert compression effects generating blood flow disorders. The paracondylar process is located at the insertion of rectus capitis lateralis, an important surgical landmark, which could be affected by the presence of the paracondylar process, thus leading to possible difficulties in orientation and iatrogenic trauma. This case contributes to extending the knowledge regarding anatomical variations, being of great use to the contemporary medical field, especially surgery.