Upper cervical ossicles in Down syndrome.

Six patients with upper cervical spine ossicles and Down syndrome from a study population of 184 are described. The average age was 20.6 years at the time of diagnosis. Three of the patients were involved in tumbling. Radiographic anatomy of the ossicles and the dens, as well as serial radiographs in three of the six patients, suggest that this represents an avulsion of the upper end of the dens rather than an occipital vertebrae, ossiculum terminale, or os odontoideum, as previously described. The authors advocate restriction of high-risk activities for all patients with Down syndrome.