Asymmetric atlas assimilation and potential danger to the brainstem: A case report

Atlas is the first cervical vertebra. It does not have a body like other cervical vertebrae. It has two transverse processes, each one of which bears a foramen transversarium. The vertebral artery passes through this foramen. It has two lateral masses which articulate with the occipital condyles to form atlanto-occipital joints. Rarely, the atlas vertebra fuses with the occipital bone. We observed a potentially dangerous incomplete occipitalization of the atlas vertebra during osteology demonstration classes. The fusion resulted in reducing the diameter of foramen magnum approximately by 25%. The knowledge of this variation may be of importance to orthopedic surgeons, neurosurgeons, radiologists and anthropologists. Copyright Internet Scientific Publications, LLC., 1996 to 2009.