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Neuroradiology Case of the Week
Case 313
Ashwani K. Sharma, MD and P-L Westesson, MD, PhD, DDS
Clinical
Presentation: A 5-year-old female was involved in a high speed motor vehicular collision and was found with loss of consciousness and pulseless at the scene.
Imaging Findings: Lateral radiographic findings in atlanto-occipital distraction injuries include soft-tissue swelling and pathologic convexity of the soft tissues anterior to C2 (generally greater than 10 mm in thickness), a basion-dens interval greater than 12 mm, or a basion–posterior axial line interval more than 12 mm anterior or 4 mm posterior to the posterior axial line [1].
Axial CT can help detect condylar fractures, which are often occult on conventional radiographs. Coronal and parasagittal reformatted images can show widening or incongruity of the articulation between the occipital condyles and the lateral masses of C1 as well as fractures of the basion [1].
Sagittal or coronal MR imaging with T2-weighted or STIR sequences can easily demonstrate prevertebral soft-tissue swelling as well as fluid within the articular capsules, nuchal ligament, and interspinous ligaments [1].
Complications including epidural hematoma, spinal cord injury, and brainstem compression can also be detected [1].
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Figure 1A-D: Sagittal and coronal reconstruction images of CT scan of neck revealed, bilateral widening of the atlanto-occipital joints with anterior displacement of the occipital condyles relative to the opposing atlantal articular masses and widened basion-dens distance. Bilateral jumped facets are also noted at C7/T1 level. |
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Figure 2A-C: Sagittal reconstruction of normal cervical spine for comparison. Note normal alignment of the occipital condyles and lateral masses of C1. Note normal joint space between them and normal basion and dens distance. |
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Figure 3A & B: Sagittal T1 and T2-weighted images of the cervical spine, reveal altered signal changes in the brainstem and cervical cord resulting from distracting injury of skull base and representing combination of contusion, laceration and ischemia. Posterior longitudinal ligament from basion to dens is lax and show loss of continuity suggesting ligamentus injury. Marked thickening of the prevertebral soft tissue is noted at the skull base. |
Diagnosis: Atlanto-occipital distraction
Discussion: The articulations of the craniocervical junction are bound and supported by several ligaments, including the anterior longitudinal ligament, the anterior atlantoaxial and atlanto-occipital ligaments, the cruciform ligaments, the alar ligaments, and the tectorial membrane.
Cervical spine fractures in the pediatric population differ distinctly from those occurring in adults. Children have the potential for growth and remodeling after injury, and in many ways are more resilient to traumatic injuries. Cervical spine injuries in children younger than 11 years tend to involve the upper cervical spine, whereas the trend in older children is similar to the adult pattern of injury to the lower cervical spine [2].
Osteoligamentous injuries at the craniocervical junction are uncommon but are of critical clinical importance. Injury to the upper cervical spine occurs frequently in fatal motor vehicle accidents, particularly among pedestrians and motorcyclists [3]. Likely mechanisms include violent distractive hyperflexion or hyperextension with or without associated rotation.
Ligamentous atlanto-occipital dislocation, displaced occipital condyle fractures with alar ligament avulsion, and tectorial membrane disruption account for most distraction injuries between the occiput and C1. Werne [4] demonstrated that disruption of both the tectorial membrane and the alar ligaments is required to produce isolated atlanto-occipital dislocation.
In fatal cases of atlanto-occipital dislocation, the most common spinocerebral injuries include lacerations of the pontomedullary junction (75%), contusion or laceration of the caudal medulla and rostral spinal cord (42%), and stretching or laceration of the midbrain (33%) [1]. Subarachnoid hemorrhage is common but may be minimal [5]. Subdural hemorrhage is seen in 16% of cases. Vasospasm and dissection of the internal carotid and vertebral arteries have been documented at angiography in several survivors of atlanto-occipital dislocation who did not have significant injuries to the spinal cord or brainstem [6]. MR or CT angiography noninvasively demonstrate vascular injury.
References:
- Deliganis AV, Baxter AB, Hanson JA, Fisher DJ, Cohen WA, Wilson AJ, Mann FA. Radiologic spectrum of craniocervical distraction injuries. Radiographics. 2000 Oct;20 Spec No:S237-50. [Medline] Erratum in: Radiographics 2001 Mar-Apr;21(2):520.
- Goss DG, Abdu WA. Distraction-flexion injury in a neurologically intact pediatric patient treated nonoperatively: case study. Spine. 2001 Sep 1;26(17):1932-5. [Medline]
- Tepper SL, Fligner CL, Reay DT. Atlanto-occipital disarticulation: accident characteristics. Am J Forensic Med Pathol. 1990 Sep;11(3):193-7. [Medline]
- Werne S. Studies in spontaneous atlas dislocation. Acta Orthop Scand Suppl. 1957;23:1-150. [Medline]
- Adams VI. Neck injuries. II. Atlantoaxial dislocation--a pathologic study of 14 traffic fatalities.J Forensic Sci. 1992 Mar;37(2):565-73. [Medline]
- Lee C, Woodring JH, Walsh JW. Carotid and vertebral artery injury in survivors of atlanto-occipital dislocation: case reports and literature review. J Trauma. 1991 Mar;31(3):401-7. [Medline]
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