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Os odontoideum

Case contributed by: Dr Frank Gaillard

Presentation:

Occasional long-track neurological symptoms.

Patient Data:

Age: 11
Gender: Male
Modality: X-ray
Modality: CT

Os odontoideum

Case Discussion:

Instability of the os odontoideum is demonstrated within the range of  motion. On the extension view the anterior arch of C1 is positioned  directly above the body of C2 and the os odontoideum is positioned just  behind the posterior vertebral line. The clivus remains aligned with  the os odontoideum indicating that the occiput, C1 and os odontoideum move together. On the flexed view the os odontoideum is positioned superior to the anterior one half of the C2 vertebral body and the anterior arch of C1 is positioned anterior to the anterior vertebral body. No other abnormality is seen.  

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