Occipitocervical Injuries

General Principles

Evaluation of the occipitocervical junction with radiographs is often inadequate to fully characterize the injury. However, in highly emergent, hemodynamically unstable situations a lateral cervical spine x-ray may be the only study that is able to be obtained until the patient is hemodynamically stabilized. In these situations, urgent imaging review centers on findings of significant deformity or instability that needs to be stabilized externally, typically with the use of a cervical orthosis and sandbags. Examples include AOD or fracture dislocation. Computed tomography (CT) with axial, coronal, sagittal, or three-dimensional reconstruction views can be extremely helpful in characterizing the presence and nature of injury. Magnetic resonance imaging (MRI) may be difficult to obtain acutely but can often provide essential visualization of neural structures and spinal canal compromise and may suggest the presence and degree of ligamentous injury. There is a risk of neurological injury with any repositioning of these patients, so care should be taken when transporting and transferring patients for studies. Only studies critical to management decisions should be pursued. In a delayed fashion, dynamic imaging with plain radiographs, CT, or MRI can be valuable in assessing stability, but should be performed carefully. Occasionally, stability is checked with real-time fluoroscopy during careful flexion and extension controlled by a qualified examiner. For example, fluoroscopic flexion/extension imaging may be helpful when there is urgent need to assess the stability of the cervical spine in an unresponsive patient, but there is still controversy about its interpretation.

Vascular injury can also occur. Considerations for performing vascular imaging include presence of neurological deficit concerning for ischemia, discrepancy between neurological findings and radiological findings, high-energy mechanism of injury, and associated spine fracture or skull base fracture that is known to pose a high risk for vascular involvement. The most commonly used criteria for obtaining vascular imaging are the expanded Denver screening criteria, which were most recently updated in 2016 by Geddes et al. Identification of vascular injury is vital because of the risk of delayed cerebral ischemia and worsening neurological deficits. These injuries are critical to identify in elderly patients, who are at a higher risk for mortality following these injuries.

Management decisions are based on the extent and stability of injury, findings of ligamentous injury, presence or progression of neurological deficits, and patient-specific factors that influence the risks associated with different treatments. Nonoperative management can include some type of rigid (halo) or semirigid (collar) orthosis. Operative management is generally indicated for injuries that are unstable, have significant potential for delayed instability, demonstrate ligamentous injury, have progressive neurological deficits, or cause significant deficits or symptoms that are not controlled with nonoperative measures.

Operative planning should include obtaining additional imaging (e.g., dedicated studies for image guidance), determining an intubation (often awake fiberoptic intubation), making an anesthesia plan, ensuring the availability of appropriate instrumentation, and arranging neurophysiological monitoring where appropriate.

Diagnosis and Management

This section will discuss injuries starting at C0 and ending at C2. However, it is important to remember that AOD is the most unstable and dangerous injury. Odontoid fractures are by far the most common injury, and are commonly seen in ground-level falls in elderly patients.

C0––Occipital Condyle Fractures

Occipital condyle fractures generally occur with axial trauma and are almost always unilateral (>90%). The most commonly cited classification system was created by Anderson and Montesano and describes three types of injuries: type I injuries are comminuted fractures that result from axial trauma; type II fractures are extensions of linear basilar skull fractures; and type III injuries are avulsion fractures of the condyle that can result from a variety of mechanisms. A recent additional classification was created by Mueller et al. in 2012. In this classification system type I injuries involved a unilateral fracture without AOD; type II is bilateral fracture without AOD, and type III is unilateral or bilateral fracture with AOD. A variety of other classification systems have been described; however, they have not gained the same popularity. These classification systems include the Harborview, Tuli, and Maserati classification system.

The incidence of occipital condyle fractures has been estimated to be between 1% and 3% of blunt craniocervical trauma cases. Although plain radiographs (usually open-mouth radiographs) may occasionally identify the injury, they have an unacceptably low sensitivity (estimated at 3.2%) and should not be relied on when the diagnosis is suspected. CT imaging with reconstruction views provides the best assessment of fracture pattern and alignment.

Occipital condyle fractures are generally stable, and therefore are typically managed with an external nonrigid orthosis (collar) until the fracture heals. Most of the literature recommends a minimum of 12 weeks with cervical orthosis; however, more recent literature suggests that 6 weeks may be sufficient in the majority of cases. Unstable occipital condyle fractures represent a form of AOD and should be treated as such.

C0–C1––Atlantooccipital Dislocations

AOD is a relatively uncommon ligamentous injury that usually results from hyperflexion and distraction during high-impact blunt trauma. AOD is more common in pediatric patients because of flatter condyles and increased ligamentous laxity in this patient population. ^, These injuries are highly unstable, frequently fatal, and usually result in significant neurological injury from stretching, compression, or distortion of the spinal cord, brainstem, and lower cranial nerves. These injuries are also associated with high levels of prehospital mortality. A study from 2010 demonstrated that AOD was the cause of death in 6% to 8% of all traffic fatalities. In addition, significant morbidity and mortality can result from associated cerebrovascular injury, which varies significantly among trauma series (0%–88%), diagnosis test used, and severity of injuries.

Lateral cervical spine radiographs may diagnose AODs but plain radiographs alone are not the diagnostic test of choice when these injuries are suspected. In addition, the frequent presence of coexisting significant head trauma can delay recognition of spinal injury. Diagnostic clues include prevertebral soft tissue swelling, increase in the basion-dens interval, and separation of the occipital condyle–to-C1 lateral mass interval ( Fig. 35.1 ). CT imaging with reconstruction views provides a better assessment of fractures and alignment than plain radiographs do. The presence of subarachnoid hemorrhage supports but does not confirm the diagnosis. MRI can be helpful for diagnosis to assess the extent of spinal cord compression and injury, and to demonstrate compressive hematoma lesions.

Whereas older methods of detecting AOD using plain radiographs have been described (e.g., Powers, Wholey, etc.), the most commonly used method is evaluation of the C1–condylar interval (CCI), which can be easily evaluated on CT. This method was first proposed by Pang et al. in 2007. ^, In this series, 89 children without AOD and 16 children with AOD underwent CT imaging with coronal reformats. Their results demonstrated a sensitivity and specificity of 100% compare with the standard radiographic measures described above. Given its high diagnostic utility, the use of CT to evaluate the CCI in pediatric patients has received a level I recommendation in the most recent Congress of Neurological Surgeons guidelines. This measurement has additionally become the most commonly used measurement in the diagnosis of AOD in the adult population, with some studies demonstrating 100% sensitivity and a false negative rate of 0% when a CCI of 1.5 mm was used.

Initial management of these injuries focuses on cervical immobilization, almost always with a halo orthosis. Cervical collars are potentially dangerous because they may produce distraction, and thereby promote further injury. Similarly, traction is specifically contraindicated, as it may fre-quently cause neurological worsening (10%, 2 of 21 patients). Nonoperative management does not provide definitive treatment of these injuries, as the primary component of the injury is ligamentous in nature; thus, they cannot be expected to heal, even with prolonged external immobilization (11 of 40 patients had nonunion or neurological deterioration). Operative stabilization consists of an occipitocervical arthrodesis with rigid internal fixation. Decompression and restoration of alignment may also be necessary to maximize neurological recovery.