Title: Cervical Spine Segmentation Defect

Imaging Findings:

Figure Plain film showing deformity involving the base of C2 (arrows).

Figure CT imaging showing continuity of deformity with cortical break and corresponding deformed lateral mass of C1 (arrows).

Clinical:

Incidental finding.

Etiology:

Anomalous development of the base of the odontoid with failure of axial spine segmentation (1).

References:

1. Keats TE. Atlas of normal roentgen variants that may simulate disease. 6th ed. St. Louis, MO: Mosby, 1992;171-173.
2. Hensinger RN. Congenital anomalies of the cervical spine. Clinical Orthopedics & Related Research. (264): 16-38, 1991 Mar.