Introduction Traumatic occipitoatlantal dislocation (OAD) is infrequent, but, with improved acute care, more commonly seen. Earlier diagnosis equals better outcome, so trauma surgeons, as first-line caregivers, must be adept at early identification. Screening for OAD should be done with cervical spine computed tomography (CT-C spine), the current standard imaging modality for acute traumatic injury. This paper delineates an easy technique classically applied to radiographs, the basion-dental-interval (BDI), for evaluating CT-C spines for OAD.
Methods Retrospective chart review performed from 1/1998-5/2009. 4 initial survivors identified and charts reviewed for time-to-diagnosis, method of diagnosis, outcome, and mechanism of injury. Initial CT-C spine images reviewed for diagnostic utility using the BDI screening method.
Results 75% (3/4) motor vehicle accidents and 25% (1/4) motorcycle accidents. Injury Severity Score (ISS) was 30-45. 100% (4/4) received CT-C spines and could be diagnosed using the BDI method. Time to diagnosis was within 24 hours. 50% (2/4) had operative intervention and were eventually discharged.
Discussion As trauma centers see more viable patients with OAD, trauma surgeons need to quickly recognize it to assure appropriate care. The BDI technique is quick and reliable using CT-C spine as the initial screening film in blunt trauma patients with significant neurological injuries.

Screening for Occipitoatlantal Dislocation in the Acute Trauma Setting

Erin Moody, MD, MBA¹ ∙ Alicia Mangram, MD, FACS¹ ∙ David Ostrow, MD² ∙ Robert Nisbet, MD³ ∙ Manual Lorenzo, MD, MBA¹ ∙ Ernest Dunn, MD¹ 

Contact: Erin Moody, MD. E-mail This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Citation: Moody E, Mangram A, Ostrow D, Nisbet R, Lorenzo M, Dunn E. Screening for occipitoatlantal dislocation in the acute trauma setting. J Surg Radiol. 2011 Jan 1;2(1). Download PDF J Surg Rad January 2011 A06.pdf 1557 Kb Received: August 15, 2010; Accepted: September 10, 2010; Published: September 16, 2010 Copyright: © 2010 Surgisphere Corporation. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Contents - Introduction - Materials and Methods - Results - Discussion - References

Introduction

Occipitoatlantal dislocation (OAD) is an injury that is typically incompatible with life. However, in the literature within recent years, there have been several case reports describing increasing numbers of survivors with the injury.1,2,3 This is largely attributed to advanced training in first responders, prompt immobilization and airway management, increased access to tertiary care centers, and implementation of standardized protocols.3,4,5,6 At our institution, we have seen an increase in initial survivors from one in 2005 to three in 2009, with two of these patients surviving to surgical intervention and discharge. We defined initial survivor as any patient that lives beyond the first 24 hours after hospital admission.

OAD can be further categorized into three general types. Type I dislocations are anteriorly displaced, and type II dislocations are vertical distraction injuries. Type II dislocations are sometimes subdivided into type IIa with vertical displacement between the occiput and atlas and type IIb with vertical displacement between the atlas and axis, but, to simplify the screening process, we will not make this distinction here. Type III dislocations describe a posterior displacement between the occipital condyles and atlas.7,8,9

Materials and Methods

Retrospective review from Jan 1998-May 2009 was performed for patients diagnosed with OAD. Medical data was analyzed for time to diagnosis, method of diagnosis, outcome, and mechanism of injury, ISS, and associated injuries.

We examined all pertinent images to ascertain reproducibility of OAD diagnosis using the BDI screening method to confirm that it is a useful diagnostic tool. The BDI was measured on initial CT’s of the cervical spine for patients with known OAD with 8.5 mm as the upper limit of normal. Measurements were made from the most inferior portion of the basion to the closest point of the superior aspect of the dens in the midsagittal plane.12,13 All films were reviewed with a neuroradiologist and/or neurosurgeon.

Results

Four initial survivors with OAD were identified. All patients were subject to blunt force trauma, 75% (3/4) motor vehicle accidents and 25% (1/4) motorcycle accidents. ISS for all patients was 30-45, and all patients received screening CT of the cervical spine.

All four initial survivors were diagnosed within twenty-four hours on CT of the cervical spine by either the neurosurgeon or radiologist on call. On review, this diagnosis was possible using the BDI screening method. Diagnosis was confirmed via direct visualization during operative intervention or autopsy. OAD was suspected in the first initial survivor based on plain film of the cervical spine, which was confirmed on CT of the cervical spine by the radiologist on call with a BDI of 23.8 mm. Significantly, this CT-C spine also showed prevertebral soft tissue swelling, which is an imaging finding associated with OAD.1,14,15 The patient was transferred to the surgical intensive care unit (SICU), where he expired on hospital day two secondary to his multiple injuries. The three remaining initial survivors all presented in 2009, were status post motor vehicle accident, and had associated neurological injuries. One patient received an initial screening CT of the cervical spine, on which OAD was not diagnosed until the neurosurgeon on call reviewed the film. This patient had a BDI of 15.6 mm. Follow-up magnetic resonance imaging (MRI) of the cervical spine confirmed OAD with injury to the cruciform ligament and ligamentum flavum, as well as swelling and hematoma in the prevertebral soft tissues. This patient was admitted to the SICU and expired on hospital day 7 secondary to complications. No operative intervention was attempted due to perceived poor prognosis.

Figure 1. A. Normal basion-dens alignment (top left). B. Anterior displacement (top right). C. Distraction/ vertical displacement (bottom left). D. Posterior displacement (bottom right).

The two remaining initial survivors underwent operative stabilization and were discharged. In one patient, an initial screening lateral cervical spine X-ray was done which failed to show the OAD or related suggestive findings, such as prevertebral soft tissue swelling. Again, the neurosurgeon on call made the diagnosis of OAD on follow-up CT of the cervical spine with a BDI of 10.5 mm. Associated findings included a fractured right occipital condyle. This patient underwent operative stabilization on hospital day 16 and was eventually discharged to a rehabilitation facility on day 67. The final patient received an initial screening CT of the cervical spine. Diagnosis was, again, made by the neurosurgeon on call with a BDI of 14.8 mm. Follow-up MRI of the cervical spine confirmed OAD and suggested transverse ligamentous injury with edema in the bilateral occipitoatlantal joints. This patient underwent operative stabilization on hospital day 15 and was discharged home on day 59. Morbidity was high for both patients secondary to related neurological injuries.

Figure 1. A. Normal CT of the cervical spine with BDI of 7.7 mm, designated by the white lines, measured the most inferior portion of the basion to the closest point of the superior aspect of the dens in the midsagittal plane (top left). B. An example of a grossly abnormal BDI (23.8 mm). OAD was later confirmed on autopsy; type I injury (top right). C. Type II injury (BDI 15.6 mm); OAD was confirmed during surgery (bottom left). D. A subtly abnormal BDI at 10.5 mm (type II injury) demonstrates the importance of this screening method as diagnosis could be missed on gross initial exam. Diagnosis was confirmed during surgery (bottom right).

Discussion

Recent advances in first responder care, better equipment, increased access to level 1 trauma centers, implementation of standardized protocols, and advances in acute care in the hospital setting have resulted in an increasing number of initial survivors with OAD, a condition that was previously associated with almost certain death. Therefore, it is reasonable to assume we may see more of these critically injured patients surviving beyond initial presentation. As such, it is imperative that trauma surgeons recognize OAD as early as possible, as failure to diagnose this injury can lead to complications and increased morbidity and mortality.10,11

Out of necessity, trauma surgeons are generally quite skilled at reading screening CT’s of the chest, abdomen, and pelvis, and head, and cervical spine for gross traumatic abnormalities and fractures. OAD, though, is sufficiently rare and has historically been associated with such a poor prognosis that most trauma surgeons have not routinely screened for it. However, as patient outcomes continue to improve, the utility of screening for this condition will increase. Trauma surgeons need to incorporate the BDI screening method into their repertoire to stay current with the accepted standard of care. Patients subjected to blunt force trauma with ISS > 30, and especially those with other neurologic injuries, should be screened for OAD using the BDI method. In addition, surgeons should routinely evaluate the occipitoatlantal joint on sagittal CT-C spine images for an obvious dislocation/dissociation. Other findings associated with OAD, which can help make the diagnosis, include paravertebral hematomas, prevertebral soft tissue swelling, joint incongruity, vertebral artery injury, capsular swelling, subarachnoid hemorrhage at the craniovertebral junction, and, rarely, fractures through cranial nerve canals.1,12,17,19

In our experience, screening lateral cervical spine radiographs provided no benefit over CT of the cervical spine as CT is fast, readily available, and a far more sensitive study (52% versus 98%, respectively for all cervical spine injuries).18,19 In addition, CT of the cervical spine more readily depicts concurrent paravertebral hematomas, prevertebral soft tissue swelling, joint incongruity, vertebral artery injury, capsular swelling, and subarachnoid hemorrhage at the craniovertebral junction, if present, which can be helpful in making the diagnosis. As mentioned above, surgeons should routinely evaluate the occipitoatlantal joint in all patients with suspected injuries of the cervical spine on sagittal CT-C spine images for an obvious dislocation/dissociation, as well as utilizing the BDI method. Recently, it was shown that 8.5 mm is the upper limits of a normal BDI on CT of the cervical spine, whereas it was commonly accepted to be 12 mm on lateral cervical spine X rays.12,16 The BDI method is one of the most sensitive described in the literature, with a distance of 8.5 mm found in >95% of the population.9,10,15 MRI of the cervical spine as of yet has little utility in the immediate screening process as it has a far slower acquisition time relative to CT and is not as widely available. However, MRI can be useful for a more specific diagnosis and description of OAD.19

Disclosure

The authors report no conflicts of interest concerning the materials or methods used in this study or the findings specified in this paper.

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