Basilar Invagination

History: 30 year old female with a history of bilateral sensorineural hearing loss. 

Single nonenhanced coronal CT through the temporal bones shows abnormal upward migration of the odontoid process and upward angling of the petrous temporal bone bilaterally.

This is the appearance of basilar invagination, of which the differential includes Paget Disease, Osteomalacia, fibrous dysplasia, achondroplasia, rickets, cleidocranial dysplasia and osteogenesis imperfecta. The diagnosis in this case was osteogenesis imperfecta, which also can cause hearing loss.