Occipital Condylar Fracture

Axial and coronal-reformatted CT images show a bone fragment inferomedial to the left occipital condyle, representing type III occipital condyle fracture. There is asymmetric widening of the left lateral atlantodental interval as well. Subsequent MRI (not shown) reveals disruption of the alar and transverse ligaments.

Facts:

• Occipital condylar fracture was likely underdiagnosed before the use of MDCT in craniocervical trauma
• Patients usually (but not necessarily) have severe head, brain and neck trauma from high-speed deceleration insults
• Incidence ranges from 3-16% of all high-speed head & neck trauma
• Complex mechanism, usually with a combination of flexion/extension, lateral bending and axial rotation of the craniocervical junction

Classification

• Most widely used one is "Anderson and Montesano"
• Type I = comminuted fracture with minimal or no displacement
• Type II = basilar skull fracture extending to the occipital condyle
• Type III = fracture with a fragment displaced medially from the inferomedial aspect into the foramen magnum (as in our case)

Note: This fracture can be easily overlooked even on MDCT. You need to think about it and look for it.

Reference:

Leone A, Cerase A, Colosimo C, et al. Occipital condylar fracture: a review. Radiology 2000;216:635-644. Free Full Text