Bilateral arcuate foramen associated with partial defect of the posterior arch of the atlas in a medieval skeleton: case report and review of the literature. Looking backward to go forward.

Purpose: We observed a complex atlas (C1) dysmorphism in a human medieval skeleton dug up from the sixth to the seventh century necropolis located in the north-eastern Italy. We analyzed such a dysmorphism in the light of pertinent literature and discussed the functional and clinical implications related to this type of C1 structural malformation.
Methods: Macroscopical and CT-SCAN examinations of the atlas were carried out.
Results: Bone findings consisted of partial aplasia of the posterior arch of the C1 accompanied by a bilateral arcuate foramen. In addition, the spinous processes of C7 and T1 were found to be bifid.
Conclusions: Although such abnormalities are supposed to be clinically inconspicuous, yet they may become challenging or even dangerous in the context of trauma. They may even complicate specific diagnostic or surgical procedures. In addition, they may cause a great number of symptoms, ranging from headache and neck pain to loss of postural muscle tone and consciousness, due to the close and complex relationship of bone structures with nerves, blood vessels, muscles, and ligaments. As a result, radiologists, clinicians, surgeons, and chiropractors should consider in their clinical reasoning the possibility that atlas dysmorphisms may occur.