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E1755. Osteogenesis Imperfecta: A Multimodality Imaging Review
Authors
  1. Karen Alexander; Children's Mercy Hospital and Clinics; University of Missouri-Kansas City
  2. Grace Mitchell; Children's Mercy Hospital and Clinics
Background
Osteogenesis Imperfecta (OI) has several forms with varying clinical severity, due to genetic abnormalities with type I collagen. Diagnosis is made by a combination of prenatal and postnatal imaging, clinical features and genetic testing. Historically, prenatal ultrasound (US) and postnatal radiographs (XR) have been the imaging modalities of choice. In recent years, prenatal magnetic resonance (MR) imaging has become more common, and the radiologist should also be familiar with its utility in OI. The purpose of this educational exhibit is to review the characteristic imaging features of OI, and to provide case examples on multiple imaging modalities to include prenatal US and MR, and postnatal XR and computed tomography (CT).

Educational Goals / Teaching Points
Hallmark features include abnormal osseous mineralization and multiple fractures. Multiple wormian bones in the skull is also common. Long bones may be shortened and angulated due to multiple fractures. Mild forms of OI may not be diagnosed until later in childhood or adolescence, usually secondary to multiple fractures. Moderate forms may present in utero or postnatally. The most severe forms are lethal due to pulmonary hypoplasia from an abnormally restrictive thorax, and are generally initially diagnosed by prenatal US.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Specific imaging findings by modality will be presented. Prenatal US performed in the second or third trimester in severe OI show diffusely decreased bone echogenicity with resultant abnormal exceptional visualization of brain anatomy, skull deformation, angulated long bones (classically the femur) and small chest circumference. Postnatal XR findings include long bone bowing deformities, and range from more severe short, thickened “crumpled” bones to less severe tubular, gracile bones. Additional findings include multiple wormian bones in the skull, and platyspondyly or kyphoscoliosis in the spine.Fetal MR images include many of the above features, and also allows for calculation of lung volumes. Postnatal CT, although not routinely performed, offers improved delineation of the osseous matrix, as well as of spinal anomalies, particularly at the craniocervical junction.

Conclusion
Osteogenesis Imperfecta is a skeletal dysplasia encompassing multiple types with varied clinical severity. Diagnosis relies on clinical, genetic and imaging findings, with the latter including typical features on prenatal US, prenatal MR, and postnatal-adolescent XR. The radiologist should be familiar with these features in order to assist in early diagnosis.