E2460. Pictorial Essay of Craniovertebral Junction Anomalies
  1. Bhanupriya Singh; Lohia Institute of Medical Sciences
To outline a few characteristic congenital anomalies of the CVJ in the form of a pictorial presentation. The Craniovertebral junction (CVJ) is a collective term that refers to the occiput, atlas, axis and supporting ligaments which encloses soft tissue structures of the cervical medullary junction.(1) A variety of congenital anomalies with the potential for causing neurological deficits occur in this region.(2) Computed Tomography and Magnetic Resonance Imaging are rewarding in the detailed evaluation and diagnosis of common and uncommon abnormalities of the CVJ.(1)

Educational Goals / Teaching Points
Multiplanar reconstruction in coronal & sagittal planes were done after obtaining axial CT images. Craniometric measurements used in radiologic assessment of CVJ anomalies include the Chamberlain line, Wackenheim clivus baseline, Welcher basal angle, and atlantooccipital joint axis angle. A pictorial representation of few of the representative congenital anomalies of CVJ are included in this study. Findings include: Congenital Anomalies of Occiput Condylar hypoplasia and Atlanto occipital assimilation Congenital anomalies of atlas Posterior arch hemiaplasia and aplasia Split Atlas Fusion anomaly of Atlas Congenital anomalies of axis Odontoid hypoplasia Os odontoideum Persistent ossiculum terminale Basilar Invagination Klippel Fliel Syndrome Platybasia Atlanto axial instability

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Occipital condylar hypoplasia Short, flat occipital condyles Widening of atlanto occipital joint axis angle Normal range : 124 to 127 ° Skull base is flattened and ascends medially Atlanto occipital assimilation Failure of segmentation between skull and first cervical vertebra Complete or partial Invariably results in basilar invagination In some cases may be associated with sudden death Posterior arch hemiaplasia Axial CT image shows absence of the right posterior arch of atlas Aplasia of posterior arch of C1 with persistent posterior tubercle Axial CT image shows absence of posterior arch of atlas and persistent posterior tubercle.

Craniovertebral junction is a unique transition between the mobile vertebral column and fixed cranium. A thorough understanding of the anatomy and anomalies is necessary for appropriate treatment planning. This presentation has focused on outlining few of the congenital anomalies of the CVJ using representative MR or CT images.