Figure 6

(patient 2) Sagittal reformatted multiplanar computed tomography of the craniocervical junction showed a hyperplastic odontoid process. The tip of the dens projected 4.8 mm above a line joining the back of the hard palate to the lowest point of the occipital squama (McGregor line). A mild basilar invagination was therefore present. Note the increased bone density of the posterior vertebral elements.