1. Critical Imaging Findings of Craniocervical Junction Injuries for the In-Training Resident
Patrick Sanchez, Duy Bui
ASNR 2016 Annual Meeting
UC Davis Medical Center
Presentation ID 2250

2. Disclosures
I have no relevant financial disclosures to report.

3. Purpose
The purpose of this educational exhibit is to provide a focused review of the anatomy, mechanisms of injury, and imaging findings of craniocervical junction injuries. An emphasis will be placed on direct and indirect imaging findings critical for the in-training resident to recognize.

4. Significance
The craniocervical junction (CCJ) is critical for maintaining cervical spine stability
Nearly 1/3 of all cervical spine injuries involve the CCJ
Findings are often radiographically dramatic however may be subtle
Injuries often portend substantial morbidity but are potentially survivable
Primary imaging modalities include CT and MR

5. Basic Anatomy- Bones Lateral Atlantoaxial joints
Middle Atlantoaxial Joint
Middle Atlantoaxial joint
Anterior arch of C1 to odontoid process
Function- Rotation
Most mobile portion of cervical spine
Atlanto-occipital Joint
Atlanto-Occipital joint
Occipital condyles to superior surface of C1 lateral masses
Function- Flexion/Extension
Lateral Atlantoaxial Joint
Lateral Atlantoaxial joints
Lateral masses of C1 and C2
Function- Lateral flexion

6. Middle Atlantoaxial Joint
Atlanto-occipital Joint
Lateral Atlantoaxial Joint

7. Anatomy- Ligaments
Ligamentous structures provide a bulk of CCJ stabilization
The transverse/alar ligaments and tectorial membrane are the most important stabilizers
Ligamentous structures can be divided into those intrinsic to the CCJ and additional extrinsic supporting structures
Intrinsic
Odontoid ligaments (apical, alar)
Cruciate ligaments (transverse, superior/inferior crura)
Anterior/Posterior longitudinal ligaments
Tectorial membrane
Extrinsic
Nuchal ligament
Ligamentum flavum
Anterior and posterior atlanto-occipital membranes

8. Basic Anatomy- Ligaments
Apical Ligament- Joins the apex of the dens to the anterior margin of the foramen magnum. Along with alar ligaments limits axial rotation of the CCJ.
Apical Ligament
Tectorial Membrane
Tectorial Membrane- Superior extension of posterior longitudinal ligament. Attaches from posterior C2 body to anterior foramen magnum. Limits excessive extension.
Basic Anatomy- Ligaments
Atlanto-occipital Joint Capsule
Anterior Longitudinal Ligament
Anterior Longitudinal Ligament- Traverses the anterior vertebral bodies extending from the C1 anterior tubercle downward.
Posterior Atlanto-occipital Membrane
Lateral Atlantoaxial Joint Capsule
Posterior Longitudinal Ligament
Ligamentum Flavum

9. Alar Ligaments
Alar- paired ligaments which attach the posterolateral dens to the medial occipital condyles. Limits excessive rotation and lateral flexion.
Occipital Condyles
C1 Lateral Masses
Transverse Ligament
Transverse Ligament- attaches to lateral masses of C1 and posterior aspect of odontoid process. Divides C1 arch into anterior and posterior compartments. Allows axial rotation.

10. Lateral Mass C2
Odontoid Process
Transverse Ligament

11. Diagnostic Evaluation
CT – Initial imaging modality of choice. Evaluation of bony injury and limited evaluation of soft tissues.
Indicated in the setting of trauma with focal neurologic deficit, c-spine tenderness, altered consciousness, intoxication, or distracting injury
MR – Evaluation of soft tissue and ligamentous injury, spinal cord compression
Guidelines for utilization are less clear
Often at discretion of treating physician
Common indications include high energy trauma, unreliable neurologic exam, +/- CCJ anomaly on CT
Patients whose neurologic status cannot be evaluated within 48hrs of injury
Treatment planning for unstable cervical spine

12. Injury Patterns Bone fractures Ligament disruption Combination
Potential to heal with conservative treatment
Ligament disruption
Potentially unstable, may require surgery
Often the result of rotational and shearing forces
Can be disrupted by fracture near attachment sites, avulsion injuries, or intrasubstance tears
Combination
Most injuries at the CCJ are a combination of both
Following will be a series of examples of bone and ligamentous injuries of the CCJ.

13. Grade 2 Occipital Condylar Fracture
Anderson and Montesano described 3 types of occipital condyle fracture based on morphology and injury mechanism.
Grade 1- Compression fracture with impaction
Grade 2- Linear condyle fracture. Associated with direct blow.
Grade 3- Avulsion injury. Secondary to rotational injury.
Implies injury of alar ligament
Often requires surgical intervention
Grade 3 Occipital Condylar Avulsion Fractures

14. Atlas C1 Arch Fracture
AKA Jefferson Fracture
Classically from an axial loading along the axis of the cervical spine although it can also occur secondary to hyperextension or flexion injuries.
Anterior/Posterior arch are weakest links.
Sometimes associated with transverse ligament injury.

15. Type 1 Odontoid Fractures
3 subtypes have been described based on the fracture site.
The mechanism of injury is variable.
Type 1- Avulsion fracture from tip of the dens at insertion of alar ligaments
Type 2- Fracture at base of dens or above junction with body
Often requires surgery
Type 3- Fracture extends into body of atlas

16. Type 2 Dens Fracture
Type 3 Dens Fracture

17. Cases
We will now exam 3 separate cases demonstrating a combination of bone and ligament injuries at the CCJ.
Complex CCJ Ligamentous Injury
Pediatric CCJ Dissociation Injury
Atlanto-occipital Subluxation Injury

18. 1. Complex CCJ Ligamentous Injury
There are associated paired apical ligament tears on this coronal proton density MR image.
Coronal CT scan demonstrates Type 3 occipital condyle avulsion fractures.

19. The Sagittal T2 MR image demonstrates several additional midline ligament disruptions.
Partial tectorial membrane tear
Anterior longitudinal ligament complex tear
Ligament disruptions contribute to an acute spinal cord compression.

20. 2. Pediatric CCJ Dissociation Injury
Sagittal CT images demonstrate vertical widening of the atlanto-occipital and lateral atlantoaxial joints without fracture.

21. Sagittal T2 weighted MR images confirm atlanto-occipital and atlantoaxial joint space widening with fluid in the joint spaces.
The apical ligament is torn and there is stripping of the tectorial membrane from the clivus.
Coronal proton density images demonstrate a right alar ligament tear.
Disruption of the anterior longitudinal ligament complex.

22. 3. Atlanto-occipital Subluxation
Sagittal CT images demonstrate widening of the atlanto-occipital joints with anterior displacement of the occipital condyles to C1 lateral masses. There is an associated occipital condyle fracture and fracture through the C1 anterior arch.

23. Sagittal T2 and Axial proton density MR images demonstrate additional ligamentous injuries which could not be seen on the CT.
Thinning and partial disruption of the tectorial membrane.
Bilateral alar ligament tears associated with occipital condylar displacement and fractures.
Disruption of the anterior longitudinal ligament complex.

24. The patient survived and was subsequently treated with an occipital to C2 fusion as seen on this Sagittal CT image.

25. Take Away Points
CCJ injuries are now more commonly imaged as injury management in the field has improved.
Understanding normal anatomy of the CCJ is critical to describe injury patterns.
CT exams may demonstrate only some of the injuries and MRI is crucial to fully evaluating the soft tissue and ligamentous structures.
Understanding common injury patterns aids in the recognition and diagnosis of additional injuries.

26. References
Riascos R, Bonfante E, Cotes C, et al. Imaging of Atlanto-Occipital and Atlantoaxial Traumatic Injuries: What the Radiologist Needs to Know. Radiographics 2015;35:
Joaquim AF, Patel AA. Craniocervical Traumatic Injuries: Evaluation and Surgical Decision Making. Global Spine J 2011;1:37-42
Junewick JJ. Pediatric Craniocervical Junction Injuries. AJR 2011;196:
Smoker W. Craniovertebral Junction: Normal Anatomy, Craniometry, and Congenital Anomalies. Radiographics 1994;14:
Deliganis AV,Baxter AB, Hansen JA, et al. Radiologic Spectrum of Craniocervical Distraction Injuries. Radiographics 2000; 20:S237-S250
Rojas CA, Bertozzi JC, Martinez CR, Whitlow J. Reassessment of the Craniocervical Junction: Normal Values on CT. AJNR 2007; 28: