A Rare Late Presentation of Os-Odontoideum with Severe Progressive Myelopathy

“Os odontoideum” is a Latin term for “a tooth-like bone”. Fielding et al classified os odontoideum into dystopic and orthotopic, based on the relationship of the odontoid process to the axis and the clivus3. The ossicle is identified as orthotopic when it is located at its normal position posterior to the anterior arch of C1 and dystopic when it is located in a displaced position and usually fused with the basion. The small odontoid process is separated from the ossicle which is usually lying cranial to the superior facets of C21.