Presentation

61 M who presented after a high speed motorcycle collision

Diagnosis

• Type III dens fracture
• Atlantoaxial dissociation with C1-C2 posterior ligamentous disruption
• Ventral epidural hematoma at the site of fracture

Key Findings

• type III dens fracture extending to and involving the right foramen transversarium
• Nondisplaced fracture of the right C7 superior facet.
• There is retropulsion of the dens fracture fragments with disruption of the anterior longitudinal ligament and buckling and likely disruption of the posterior longitudinal ligament
• Retropulsed dens fragment result in effacement of the ventral thecal sac with cord contact. No abnormal cord signal.
• Circumferential epidural hematoma extends from C2 through C3-4
• Widening of C1-C2 interspinous space with extensive posterior paraspinous increased STIR signal
• Disruption and bilateral widening of C1-C2 lateral mass articulations.
• Increased STIR signal at site of right C6-7 facet articulations corresponding to site of right C7 superior facet fracture.

Discussion

• Because the type III dens fracture involves right foramen transversarium, this patient would also be a candidate for a CTA neck to evaluate for BCVI
• Widening of C1-C2 interspinous space, subtle bilateral widening of C1-C2 lateral mass articulations, and extensive posterior paraspinous increased STIR signal are all findings that should raise the suspicion for atlantoaxial dissociation with severe posterior ligamentous disruption. Note that some of these findings can also be appreciated on the CT, though the soft tissue injuries make them more obvious on MRI.
• An excellent review on the imaging findings of trauma to the craniocervical junction can be found here: https://pubs.rsna.org/doi/10.1148/rg.2015150035