Presentation
Road traffic accident
Patient Data
A well corticated oval ossicle is seen above the body of C2, below the clivus, and behind the anterior arch of C1, corresponding to the os odontoideum.
A midline defect of the posterior arch of C1 (failure of midline fusion of the two hemiarches), type A according to the Currarino classification.
Note calcification within the anterior atlanto-axial ligament.
No cerebral or cervical spine traumatic lesion seen in this case.
Case Discussion
Os odontoideum is considered as an anatomic variant of the odontoid process of C2. It belongs to the group of the skeletal “don’t touch” lesions. The differential diagnosis includes:
- Bergmann's ossicle (persistent ossiculum terminal)
- odontoid fracture (type 2)
Congenital anomalies of the posterior atlas arch are benign anatomical variants and should not be confused with fracture or dislocation.
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