MRI of Traumatic Injury to the Craniovertebral Junction
MRI of Traumatic Injury to the Craniovertebral Junction
Object The craniovertebral junction (CVJ) is unique in the spinal column regarding the degree of multiplanar mobility allowed by its bony articulations. A network of ligamentous attachments provides stability to this junction. Although ligamentous injury can be inferred on CT scans through the utilization of craniometric measurements, the disruption of these ligaments can only be visualized directly with MRI. Here, the authors review the current literature on MRI evaluation of the CVJ following trauma and present several illustrative cases to highlight the utility and limitations of craniometric measures in the context of ligamentous injury at the CVJ.
Methods A retrospective case review was conducted to identify patients with cervical spine trauma who underwent cervical MRI and subsequently required occipitocervical or atlantoaxial fusion. Craniometric measurements were performed on the CT images in these cases. An extensive PubMed/MEDLINE literature search was conducted to identify publications regarding the use of MRI in the evaluation of patients with CVJ trauma.
Results The authors identified 8 cases in which cervical MRI was performed prior to operative stabilization of the CVJ. Craniometric measures did not reliably rule out ligamentous injury, and there was significant heterogeneity in the reliability of different craniometric measurements. A review of the literature revealed several case series and descriptive studies addressing MRI in CVJ trauma. Three papers reported the inadequacy of the historical Traynelis system for identifying atlantooccipital dislocation and presented 3 alternative classification schemes with emphasis on MRI findings.
Conclusions Recognition of ligamentous instability at the CVJ is critical in directing clinical decision making regarding surgical stabilization. Craniometric measures appear unreliable, and CT alone is unable to provide direct visualization of ligamentous injury. Therefore, while the decision to obtain MR images in CVJ trauma is largely based on clinical judgment with craniometric measures used as an adjunct, a high degree of suspicion is warranted in the care of these patients as a missed ligamentous injury can have devastating consequences.
The craniovertebral junction (CVJ) is an anatomically complex region bound together by an intricate network of ligaments and articulations, all of which contribute to its overall stability. The bony elements of the CVJ are the occipital bone including the clivus and occipital condyles, as well as the first 2 cervical vertebrae, the atlas and axis. The major ligamentous elements of the CVJ located anterior to the spinal cord consist of accessory atlantoaxial, cruciate, alar, and apical odontoid ligaments; and the anterior atlantooccipital membrane. Posterior to the spinal cord, the capsular joint ligaments and the posterior atlantooccipital membrane provide stability to the CVJ. The anterior and posterior atlantooccipital membranes are continuations of the anterior and posterior longitudinal ligaments that run the length of the vertebral column. While the bony and ligamentous structures provide CVJ stability, these articulations allow great freedom of movement, permitting 25% of neck flexion-extension and up to 40° of head rotation.
Although the exact proportion of cervical spine fractures that involve this region is not known, sources estimate that a third to half of all cervical spine injuries involve the CVJ. Many patients with CVJ trauma have an altered level of consciousness or other injuries that can make the physical examination difficult or less reliable. This can lead to delayed or missed diagnosis of CVJ injuries. Conventional radiographs or CT scans can reveal bony anatomy with great detail and have a high sensitivity for fractures. However, many bony injuries of the CVJ are not inherently biomechanically unstable and therefore do not require surgical intervention. Conversely, patients with unstable CVJ injuries requiring surgery may not necessarily have fractures. Therefore, determining the integrity of ligamentous structures of the CVJ is paramount in deciding whether surgical stabilization is necessary. Prior to the widespread use of MRI in the evaluation of spinal trauma, methods to determine CVJ instability were based on bony measurements. While these methods, referred to as craniometrics, are useful, MRI is playing an ever greater role in CVJ trauma, and its use continues to increase over time.
In the current paper, we review the current literature on the MRI evaluation of patients with CVJ trauma. Additionally, we present 8 illustrative cases from our institution to highlight key MRI findings indicative of unstable ligamentous injury and the need for surgical intervention.
Abstract and Introduction
Abstract
Object The craniovertebral junction (CVJ) is unique in the spinal column regarding the degree of multiplanar mobility allowed by its bony articulations. A network of ligamentous attachments provides stability to this junction. Although ligamentous injury can be inferred on CT scans through the utilization of craniometric measurements, the disruption of these ligaments can only be visualized directly with MRI. Here, the authors review the current literature on MRI evaluation of the CVJ following trauma and present several illustrative cases to highlight the utility and limitations of craniometric measures in the context of ligamentous injury at the CVJ.
Methods A retrospective case review was conducted to identify patients with cervical spine trauma who underwent cervical MRI and subsequently required occipitocervical or atlantoaxial fusion. Craniometric measurements were performed on the CT images in these cases. An extensive PubMed/MEDLINE literature search was conducted to identify publications regarding the use of MRI in the evaluation of patients with CVJ trauma.
Results The authors identified 8 cases in which cervical MRI was performed prior to operative stabilization of the CVJ. Craniometric measures did not reliably rule out ligamentous injury, and there was significant heterogeneity in the reliability of different craniometric measurements. A review of the literature revealed several case series and descriptive studies addressing MRI in CVJ trauma. Three papers reported the inadequacy of the historical Traynelis system for identifying atlantooccipital dislocation and presented 3 alternative classification schemes with emphasis on MRI findings.
Conclusions Recognition of ligamentous instability at the CVJ is critical in directing clinical decision making regarding surgical stabilization. Craniometric measures appear unreliable, and CT alone is unable to provide direct visualization of ligamentous injury. Therefore, while the decision to obtain MR images in CVJ trauma is largely based on clinical judgment with craniometric measures used as an adjunct, a high degree of suspicion is warranted in the care of these patients as a missed ligamentous injury can have devastating consequences.
Introduction
The craniovertebral junction (CVJ) is an anatomically complex region bound together by an intricate network of ligaments and articulations, all of which contribute to its overall stability. The bony elements of the CVJ are the occipital bone including the clivus and occipital condyles, as well as the first 2 cervical vertebrae, the atlas and axis. The major ligamentous elements of the CVJ located anterior to the spinal cord consist of accessory atlantoaxial, cruciate, alar, and apical odontoid ligaments; and the anterior atlantooccipital membrane. Posterior to the spinal cord, the capsular joint ligaments and the posterior atlantooccipital membrane provide stability to the CVJ. The anterior and posterior atlantooccipital membranes are continuations of the anterior and posterior longitudinal ligaments that run the length of the vertebral column. While the bony and ligamentous structures provide CVJ stability, these articulations allow great freedom of movement, permitting 25% of neck flexion-extension and up to 40° of head rotation.
Although the exact proportion of cervical spine fractures that involve this region is not known, sources estimate that a third to half of all cervical spine injuries involve the CVJ. Many patients with CVJ trauma have an altered level of consciousness or other injuries that can make the physical examination difficult or less reliable. This can lead to delayed or missed diagnosis of CVJ injuries. Conventional radiographs or CT scans can reveal bony anatomy with great detail and have a high sensitivity for fractures. However, many bony injuries of the CVJ are not inherently biomechanically unstable and therefore do not require surgical intervention. Conversely, patients with unstable CVJ injuries requiring surgery may not necessarily have fractures. Therefore, determining the integrity of ligamentous structures of the CVJ is paramount in deciding whether surgical stabilization is necessary. Prior to the widespread use of MRI in the evaluation of spinal trauma, methods to determine CVJ instability were based on bony measurements. While these methods, referred to as craniometrics, are useful, MRI is playing an ever greater role in CVJ trauma, and its use continues to increase over time.
In the current paper, we review the current literature on the MRI evaluation of patients with CVJ trauma. Additionally, we present 8 illustrative cases from our institution to highlight key MRI findings indicative of unstable ligamentous injury and the need for surgical intervention.
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