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Atlanto-occipital Dislocation

Sagittal reconstructed computed tomography (CT) of the cervical spine is notable for craniocervical dislocation (Fig. 16-1).

Diagnosis

Atlanto-occipital dislocation

Treatment

Although the patient’s vital signs were revived, she was declared brain dead.

Discussion

Atlanto-occipital dislocation is a common site of fatal injury in children sustaining significant upper cervical trauma. The fatality results from a hyperextension-distraction injury of the craniocervical junction leading to shearing of the cervicomedullary junction and respiratory arrest. While the mechanism is typically traumatic, it may be encountered in atraumatic cases such as Down syndrome or rheumatoid arthritis. The tectorial ligaments, which hold the condyles to the atlas, are torn.

Atlanto-occipital dislocation is a radiographic diagnosis. Several measurements are described to establish the diagnosis. However, the condition is often grossly evident based on radiographs, the patient’s poor clinical condition, and the mechanism of injury. The Powers ratio takes the distance from the basion to the midvertical portion of the posterior laminar line of the atlas (BC), over the distance from the opisthion to the midvertical portion of the posterior surface of the anterior ring of the atlas (OA). If BC/OA is 1 or greater, the diagnosis is secured.