Occipitoatlantal Dislocation (Craniovertebral Dissociation)

This is almost always fatal, with postmortem studies showing it to be the leading cause of death in motor vehicle accidents; rare survivors have severe neurologic deficits ranging from complete C1 flaccid quadriplegia to mixed incomplete syndromes such as Brown-Séquard.

This is twice as common in children, owing to the inclination of the condyles.

It is associated with submental lacerations, mandibular fractures, and posterior pharyngeal wall lacerations.

It is associated with injury to the cranial nerves (the abducens and hypoglossal nerves are most commonly affected by craniocervical injuries), the first three cervical nerves, and the vertebral arteries.

The cervicomedullary syndromes, which include cruciate paralysis as described by Bell and hemiplegia cruciata initially described by Wallenberg, represent the more unusual forms of incomplete spinal cord injury and are a result of the specific anatomy of the spinal tracts at the junction of the brainstem and spinal cord. Cruciate paralysis can be similar to a central cord syndrome, although it normally affects proximal more than distal upper extremity function. Hemiplegia cruciata is associated with ipsilateral arm and contralateral leg weakness.

Mechanism is a high-energy injury resulting from a combination of hyperextension, distraction, and rotation at the craniocervical junction.

The diagnosis is often missed, but it may be made on the basis of the lateral cervical spine radiograph:

• The tip of odontoid should be in line with the basion.

• The odontoid–basion distance is 4 to 5 mm in adults and up to 10 mm in children.

• Translation of the odontoid on the basion is never >1 mm in flexion/extension views.

• Powers ratio (BC/OA) should be <1 (Fig. 9.5).

• In adults, widening of the prevertebral soft tissue mass in the upper neck is an important warning sign of significant underlying trauma and may be the only sign of this injury.

• Fine-cut CT scans with slices no more than 2 mm wide are helpful to understand articular

  incongruities or complex fracture patterns more clearly. MRI of the craniovertebral junction is indicated for patients with spinal cord injury and can be helpful to assess upper cervical spine ligamentous injuries as well as subarachnoid and prevertebral hemorrhage.

   

   

   

Classification based on the position of the occiput in relation to C1 is as follows:

Type I: Occipital condyles anterior to the atlas; most common

Type II: Condyles longitudinally dissociated from atlas without translation; result of pure distraction

Type III: Occipital condyles posterior to the atlas

The Harborview classification attempts to quantify stability of craniocervical junction. Surgical stabilization is reserved for types II and III injuries.

Type I: Stable with displacement <2 mm

Type II: Unstable with displacement <2 mm

Type III: Gross instability with displacement >2 mm

Immediate treatment includes halo vest application with strict avoidance of traction. Reduction maneuvers are controversial and should ideally be undertaken with fluoroscopic visualization.

Long-term stabilization involves fusion between the occiput and the upper cervical spine.