Spontaneous rotatory atlantoaxial dislocation without neurological compromise in a child with Down syndrome: a case report.

Spontaneous atlantoaxial dislocation is a rare recognised complication of Down syndrome. In the majority of cases, dislocation takes place in an anteroposterior direction and is often associated with abnormalities of odontoid development or ossification. Rotatory atlantoaxial dislocation is extremely rare in Down syndrome and this is to our knowledge the first reported case in which modern imaging methods have been described; surface shaded reformats derived from a multislice CT scan were of fundamental importance in making the diagnosis.