Atlanto-occipital dissociation - Traynelis type 1

Case contributed by Craig Hacking


High speed motor vehicle accident. GCS 3 and intubated at the scene.

Patient Data

Age: 25 years
Gender: Female

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.
Anterior mild anterior subluxation of C3 on C4 and C4 on C5. The adjacent facet joints are intact. Mild widening of the C5/6 and C6/7 intervertebral disc spaces - this may represent an acute injury or be long standing (as there has been prior laminectomy at C6/7.)

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

Suspected anterior epidural hematoma 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 hematoma. ETT and NGT in situ.

CTA neck vessels


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 edema throughout the neck involving multiple compartments particularly anteriorly anterior to the thyroid gland. The thyroid gland appears edematous.

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 edema 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 hematoma 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.

Chronic appearing posterior midline cord cleft at the level of C6 correlates with history of previously repaired spina bifida. Mild prominence of the adjacent central canal at the cervicothoracic junction. C6 and C7 laminectomies noted.

High signal on the sagittal STIR sequence at C6/C7 disc level and to a lesser extent at C5/C6 disc level may be degenerative in origin, with differential of undisplaced traumatic involvement. No obvious increased acute fluid is noted within the facet joints to suggest disruption. Sagittal STIR sequences throughout the remaining thoracic, lumbar and sacral spine demonstrate no acute marrow edema. Dependent layering within the sacral spinal canal is in keeping with intrathecal subarachnoid blood products.

Traumatic lung changes in the visualized upper lung fields, more prominent on the right where there is a posterior pneumothorax and patchy consolidation. Left ICC partially included.

Case Discussion

Intracranial injuries were also present and the patient passed away one day later.

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