Atlanto-occipital dissociation - Traynelis type 1

Anterior dislocation of the occipital condyles relative to the lateral masses of C1 - type 1 atlanto-occipitial dislocation. Associated comminuted fractures of bilateral occipital condyles with medial displacement of the fracture fragments. The articulating process of C1 is subluxed posteriorly with marked widening of the joint space. Avulsion fracture from the anterior aspect of the left C1 articulating process. Marked widening between the basion and dens of C2. Basion dental interval 12.5 mm. Suspected injury/disruption of the anterior longitudinal ligament.

The dens is intact. Widening C1-C2 articulation suggest ligamentous injury at this level. Marked prevertebral soft tissue swelling anterior to C1 and C2 cervical vertebral bodies.

Soft tissue ossification on the left anterior aspect of the C5 vertebral body likely chronic.

Suspected anterior epidural haematoma within the upper cervical spinal canal from C1 to C5.

Subcutaneous air within the neck and prevertebral soft tissue presumably air dissecting superiorly from the pneumothorax. Low density subcutaneous fluid below the thyroid cartilage anterior to the trachea extending down into the superior mediastinum may represent an evolving subcutaneous haematoma. ETT and NGT in situ.

Limited quality study due to patient motion artefact. The carotid arteries are intact. Dominant left-sided vertebral artery. Small filling defect in the left distal vertebral artery at the level of C1. The basilar artery is intact.

Extensive subcutaneous soft tissue oedema throughout the neck involving multiple compartments particularly anteriorly anterior to the thyroid gland. The thyroid gland appears oedematous.

Atlanto-occipital dissociation with malalignment as demonstrated on CT, with widening and asymmetry (joint wider on the left) of the articulations. Complete disruption at the junction of the tectorial membrane and posterior longitudinal ligament at the level of C1/C2, with a 15 mm wide craniocaudal defect in this region. The apical ligament is disrupted. The transverse atlantal ligament posterior to the dens appears intact. Alar ligaments are difficult to identify. Diffuse posterior paraspinous soft tissue oedema throughout the cervical region in keeping with further ligamentous disruption.

High T2/FLAIR signal is present within the cervical cord on the left at the craniocervical junction, extending across midline to the right inferiorly at the level of C1. No increased susceptibility or high T1 signal products demonstrated in this cord region. Small volume adjacent epidural haematoma is not associated with significant compression of the thecal sac. Minor anterior effacement of the right cord just below this level at C1/C2 junction.