Basilar impression (BI) assessed by either plain lateral skull radiograph or computerized tomography (CT) sagittal reconstruction of the craniocervical junction is a common finding occurring in 25% of subjects with osteogenesis imperfecta (OI). It appears to occur with highest frequency in a group of subjects with OI type IV B, i.e. patients with mild/moderate liability to fractures, normal sclerae but dentinogenesis imperfecta. Neurologic signs indicating compression of posterior fossa structures occur predominantly in subjects with BI and OI type IV. Screening is recommended for all patients with OI but particularly OI type IV B.