Bone Malformation of the Cervico-Occipital Causing a Basilar Impression and Triventricular Hydrocephalus

Congenital bone malformations of the cervico-occipital hinge are rare entities. They are often asymptomatic and often incidentally discovered during imaging examinations for malformative assessment or for other indications, but they can be the cause of neurological symptoms or signs of compression in the posterior fossa. We report a case of a bony malformation of the cervico-occipital hinge in a 16-year-old girl, with no medical and surgical history or known history of trauma. This malformation associates hypertrophy of the odontoid with basilar impression, causing triventricular hydrocephalus. The diagnosis was made by the cervico-cerebral scanner requested in front of a gait disorder and an attitude of cervical hyperextension since early childhood.