Traumatic atlanto-occipital dislocation (AOD) is a rare but frequently fatal injury occurring at the craniocervical junction between the base of the skull (occiput) and the proximal cervical vertebrae (atlas) (C1) and axis (C2) (Figure 1). It is generally seen in young children and adolescents (Przybylsk et al, 1996; Hosalker et al, 2005; Garrett et al, 2010), however, this injury is not as uncommon as previously thought, as it accounts for approximately 6–8 % of all fatal traffic injuries occurring in children. Moreover, of those with a fatality that is directly related to the cervical spine injury, 20–30 % result from an AOD (Hosalkar et al, 2005; Garratt et al, 2010; Ehlinger et al, 2011).
In general, the cause is a high energy trauma—most often: a motor vehicle collision, a vehicle versus a paediatric pedestrian or a vehicle versus a child on a bicycle (Przybylski et al, 1996; Garrett et al, 2010). The energy from this trauma disrupts the ligaments and membranes that give support to the occipital cervical junction, causing a sudden and acute instability of the proximal cervical spine with possible damage to the brain stem or spinal cord. A combination of forces can cause the disruption of the supporting ligaments, including; forces directed in flexion, extension or traction, leading to the dislocation (AOD) (Hosalker et al, 2005).
Historically, only a few children survived this injury: most succumbed to their traumas before arriving at hospital emergency facilities (Przybylski et al, 1996). The first description of AOD was provided by Blackwood (1908). Over the next seven decades, only six children who survived this type of trauma have been reported in the English literature (Przybylski et al, 1996). However, many studies in recent years describe an increased survival rate among this population (Przybylski et al, 1996; Labler et al, 2004), suggesting that in the past, the recognition and management of these injuries was not as adequate, either in the field or hospital. Therefore, lifesaving measures were not started early enough. In contrast, recent recognition of AOD and improved pre-hospital care in the field by paramedics and other staff has dramatically changed the prognosis of children with these injuries. Improved pre-hospital care has increased the chances of survival and has yielded a better prognosis (Ehlinger, 2011). The improved care includes early recognition of this life–threatening injury, provision of appropriate intubation and ventilation, immobilisation of the head and neck and the use of a spine board, followed by prompt and rapid transportation to the hospital. These measures have allowed time for further diagnostic investigation, stabilisation of the patient's condition and if necessary, provision for permanent stability of the cervical spine achieved by a surgical arthrodesis (spinal fusion).
In this report, an overview of our experience with AOD over 17 years is provided and illustrated with a case report (Hosalkar et al, 2005). Finally, methods or improving pre-hospital care in the trauma field with the goal of increasing the survival rate will be discussed.
Clinical experience
Over a period of 17 years (1986–2003), a total of 16 children with AOD were seen at the Children's Hospital of Philadelphia. The mean age of this group was 7.6 years (range 1.3–16.3 years). All 16 children suffered a high energy trauma: the majority of patients were victims of a motor vehicle accident, either vehicle versus pedestrian or vehicle versus child on a bicycle. There was one case of a bicycle rider hit by a trolley, one football injury and one suicide attempt by hanging from a tree.
All patients were assessed and stabilised by paramedics following standard protocols of paediatric advanced life support. A diagnosis of craniocervical head injury and high spinal cord lesion was suspected in the field and confirmed in the emergency department (ED) in all cases. Eleven patients underwent intubation in the field and two were intubated on arrival to the ED. Eight of the 16 patients were dead either on arrival or died soon after arriving, despite aggressive resuscitation efforts by emergency care professionals. Eight patients survived long enough to be transferred to the intensive care unit (ICU) where the spine was stabilised by application of a halo-vest. These patients also received a standard high dose of intravenous steroids (30 mg/kg body weight) to control edema of the brain and spinal cord. Three of these eight patients required an urgent surgical decompression of the brain injury due to haemorrhage; all three ultimately died from complications resulting from their brain injury. The five remaining patients survived. Four of the five patients underwent a surgical arthrodesis from the occiput to C2, in order to permanently stabilise the upper cervical spine. One patient, seen earlier in the study, was managed by prolonged immobilisation in a brace and eventually gained cervical stability over time. At the time of the final follow–up, with a mean of 4.2 years following the injury, one patient improved to a neurologically normal state, and three others also achieved impressive neurologic motor recovery with improved function despite a mild residual spastic paraparesis. All three were able to walk and were very functional with all the skills needed for daily living. Unfortunately, one of the five survivors was clinically unchanged with complete spastic paraplegia and remained ventilator-dependent.
Illustrative case report
A four-year-old boy who had been struck by a motor vehicle was found unconscious at the site and in urgent need of ventilator support. He had a Glasgow Coma Scale of 3/15. Initial treatment given in the field included immediate intubation and ventilation support, a cervical collar, a spine board and rapid transfer to the ED. On arrival to the hospital, a high dose of intravenous steroids (30 mg/kg body weight) was administered. Radiographs confirmed AOD (Figure 1), as well as a fracture through the mid shaft of the right femur. Despite radiographic evidence of pulmonary contusion, spontaneous respiration was present. Prior to a transfer to the ICU, halo-vest immobilisation was performed to immobilise the cervical spine. The patient was stabilised and prepared for a surgical arthrodesis from the occiput to C2. With further investigation, magnetic resonance imaging (MRI) revealed a spinal cord contusion (Figure 2).
Three days following admission, surgical arthrodesis was done without complication and the femur fracture was reduced and stabilised by an external fixator and healed uneventfully. With follow up of the cervical spine, the occiput to C2 completely fused by the twelfth week following surgery. At this time, a considerable recovery of motor power to the right leg was observed. Using the 0–5 motor power scale, the power improved from grade 1/5 at hospital discharge to grade 4/5, recorded during the twelfth week post-operative visit. At 55 months post–surgery, follow up radiographs again showed a solid fusion (Figure 3). At this point, the patient was very functional, both at home and school. He walked remarkably well but continued to have mild spasticity and grade 4/5 power in the right lower extremity.
This child likely would not have survived without the rapid response of the paramedics in the field. Their advanced life support which included early intubation, immobilisation with a cervical brace and spine board and rapid transportation to our medical centre greatly contributed to the survival of this child.
Discussion
Atlanto-occipital dislocation is a serious injury with a high mortality and morbidity. It can be a neurologically devastating injury and is often fatal. Recently, it has been recognised that it is more common than previously thought, especially in children. AOD is seen in approximately 25–35 % of paediatric traffic fatalities (Gluncic et al, 2010) A high energy trauma, mostly occurring in traffic accidents, is usually the cause for traumatic AOD (Hosalkar et al, 2005; Garrett et al, 2010).
Mechanisms of injury
The amount of force generated from these accidents can cause injury and disruption of the ligaments and membranes that connect and support the occipital condyles to the proximal cervical vertebrae. AOD occurs primarily at the junction between the base of the skull and the atlas (C1), although frequently the interval between the atlas and axis (C2) is also involved. The disruption consequently changes the stability of the craniocervical anatomy, thus risking damage to the brain stem and/or spinal cord. The tectorial membrane, which is an extension of the posterior longitudinal ligament, the alarm ligaments and cruciate ligaments are the most important supporting structures in the paediatric cervical spine. In children, these structures are incompletely developed, thus more easily disrupted. This, in combination with incomplete development of the articular joints of the spine makes the paediatric population more vulnerable to high energy trauma. Incomplete development of the articular joints results in shallow joint configurations such as small occipital condyles and a flat orientation of all the joints. This increases the risk for instability and serious spinal injuries such as AOD following high energy trauma involving children (Henry et al, 1998; Chattar-Cora and Valenziano, 2000; Houle et al, 2001; Hosalkar et al, 2005; McElwee and Wargo, 2006; Ehlinger et al, 2011). The two possible mechanisms include hyperflexion and hyperextension. Hyperflexion disrupts the alar ligaments, with lateral flexion often acting as an additional force, whereas hyperextension results in a damaged tectorial membrane (Chattar-Cora and Valenziano, 2000; Houle et al, 2001; Gluncic et al, 2010).
Recognition
As the consequences of undetected or inadequately treated AOD can be devastating, early recognition and treatment or stabilisation of a child with this injury is of great importance. Diagnosis depends on early clinical suspicion. Clearly, it is not always easy to recognise this type of injury; however, paramedics should be highly suspicious of AOD in specific situations.
First, as outlined above, traumatic AOD is the result of high energy trauma. Therefore, every collision involving a child and a motor vehicle should arouse suspicion and should be treated as a high energy trauma (Houle et al, 2001). The structures providing stability in the paediatric cervical spine are less developed or have a different anatomy compared to adults, thus predisposing children to AOD, even in minor traumas.
Second, AOD should be suspected when a trauma with significant head injury occurs. In fact, the cause of fatality in our series was most often due to brain injury. It is clear that a serious head injury may mask the presence of AOD. Subdural, subarachnoidal or intracerebral hemorrhages can cause neurological complications that mask the neurological disabilities resulting from spinal cord damage caused by AOD. Therefore, AOD has to be suspected in every major trauma with concomitant head injury. Sometimes these intracranial haemorrhages may require neurosurgical intervention. Signs of head injury include, for example, unconsciousness, confusion, change or difference in size of eye pupils, seizures and vomiting. Also, symptoms originating from brain stem (or medullar) compression and spinal cord damage should be recognised. Furthermore, extremity weakness or paralysis may represent cord damage, in the worst case resulting in complete tetraplegia.
Provision of airway
Third, one of the most important is the cardiopulmonary status of the child as it is regulated by certain centres in the brain stem. Agonal breathing, cardiac arrhythmias and lowered blood pressure are possible signs of compression on the brain stem. However, the presence of some phonation, crying or laboured speech is an indication that this injury is incomplete, and thus may represent a potential for survival. However, this is not a reason to avoid intubation, even in the trauma field. Providing an open airway and effective ventilation is crucial.
Finally, recognising these symptoms in the field should raise the suspicion of AOD. This observation is essential in providing the best possible chance of survival for these children. In this case, one should not hesitate to stabilise the head and cervical spine in an appropriate position and provide an adequate airway. Following this, rapid transportation to the hospital is necessary. There the diagnosis can be confirmed with lateral radiographs. Magnetic resonance imaging may reveal compression of the spinal cord, disruption of supporting structures and AOD-associated atlanto-axial (C1-2) disruption. If AOD is confirmed, a surgical arthrodesis for stabilisation should be considered, as the ligamentous injury is not likely to heal spontaneously with external immobilisation.
Conclusions
In conclusion, atlanto-occipital dislocation is a serious injury that can be fatal if not recognized early or treated inadequately. Early recognition of this trauma is the key in improving the chances of survival for these children. AOD and severe head injury often occur together. Recognize one and expect the other. If there is a serious head injury, or a suspected head injury, one should immobilize the cervical spine for transport. Intubation in the field and ventilation is frequently necessary and lifesaving and immobilisation of the cervical spine can prevent further injury. Finally, efficient and rapid transport and treatment is needed. The earlier that AOD is recognized, managed and the child transported to hospital, the better the chance for survival and the better the long term prognosis for recovery.