School ager with Trisomy 21

Radiograph of atlanto occipital instability
Lateral radiograph of the cervical spine in flexion (left) shows a normal atlanto dens interval and normal relationship of the occipital condyles to the lateral masses of C1 while on extension (right) there is posterior translation of the occipital condyles in relation to the lateral masses of C1.

The diagnosis was atlanto occipital instability in a patient with Trisomy 21.