Imaging anatomy of the cranio-vertebral junction (occipito-atlanto-axial joint)

The diagnostic value of magnetic resonance imaging (MRI) is directly related to the ability to interpret differences between significant pathology and normal anatomical variations. A multidisciplinary investigation of the cranio-vertebral articulation with CT, MRI, anatomical dissections and sections, 3D reconstruction, and injections of contrast into the joint spaces has demonstrated some of the anatomical structures which can cause differences in CT and MR images. Some of the factors which can contribute to variations observed in clinical imaging include the supraodontoid bursa with varying amounts of fat or containing a Bergmann's ossicle, fat pads related to the transverse ligament or laxity of the ligament, identification of the ossiculum terminale or of the synostosis at the base of the dens, and flow patterns in the vertebral plexus of veins.