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

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.
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