IS Case 383: Atlanto-occipital dislocation

Parul Patel, MD

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2009 URMC Imaging Sciences
Publication Date: 2010-03-02

History

Patient is an 18-year-old woman status post-motor vehicle crash. Patient was the unrestrained backseat passenger and was ejected from the vehicle.

Findings

Complete atlanto-occipital dislocation.

Diagnosis

Atlanto-occipital dislocation

Discussion

Atlanto-occipital injuries range from complete atlanto-occipital or atlantoaxial dislocation to non-displaced occipital condyle avulsion fractures. The articulations of the craniocervical junction are defined by the middle atlantoaxial joint (which allows rotation of C1 and C2), and the paired lateral atlantoaxial and atlanto-occipital articulations. Injuries of the upper cervical spine occur most frequently in fatal motor vehicle accidents with the likely mechanism including violent distractive hyperflexion or hyperextension. Normal measurements for several of the bone relationships at the craniocervical junction have been determined and are useful in excluding upper cervical spine injury and are summarized below:

• Basion-dens interval < 12mm

• Anterior atlanto-dens interval < 2mm

• Lateral atlanto-dens articulation < 2-3mm side to side difference

• Basion-posterior axial line interval < 12mm posterior to basion, < 4mm anterior to basion

• Atlanto-occipital articulation 1-2mm

• Atlantoaxial articulation 2-3mm

References

1. Deliganis AV, Baxter AB, Hanson JA, et al. Radiologic spectrum of craniocervical distraction injuries. Radiographics. 2000 Oct;20 Spec No:S237-50. PMID: 11046174