Os odontoideum with cleft of the posterior arch of C1

Case contributed by Dr Ammar Haouimi


Road traffic accident

Patient Data

Age: 35 years
Gender: Male

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:

Congenital anomalies of the posterior atlas arch are benign anatomical variants and should not be confused with fracture or dislocation.

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Case information

rID: 63500
Published: 6th Oct 2018
Last edited: 14th Aug 2019
System: Spine
Inclusion in quiz mode: Included
Institution: Aurès Medical Imaging Center - Batna Algeria

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