Unilateral Facet Dislocation with Carotid Dissection
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This is an example of unilateral facet dislocation.
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And we are looking at the right side and the left side.
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So you notice that on the right side,
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the superior facet is dislocated posterior to the inferior facet.
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But on the left side,
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the superior facet is anterior to the inferior facet
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in the normal position. It's a little bit angular,
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quite normal, but it's a unilateral facet dislocation.
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With unilateral facet dislocation,
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the degree of offset of the superior vertebral body to the
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inferior vertebral body is usually less than half or
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less than one-fourth. This is grade 1 offset.
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You notice that there is widening here between the
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spinous processes and the posterior elements.
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This patient had associated injury to the spinal
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cord despite only grade 1 offset.
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The cord here is bright in signal intensity
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and has been damaged.
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You see that the patient has disruption here of the
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ligamentum flavum and the interspinous ligament.
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This is the posterior column, the third column.
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Here we have the posterior longitudinal ligament coming up,
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and then it's flapping in the breeze here.
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So this is the second column injury.
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The anterior column likely infected as well with bright
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signal intensity in the intervertebral disc.
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So injury to the spinal cord, not only that,
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but this patient also showed carotid dissection secondary
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to the trauma. It's usually not secondary to the fracture,
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which would usually affect the vertebral artery,
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but secondary to the trauma, there was a carotid dissection.
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So this is how,
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with the CT scans that show these type of offsets,
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you're going to recommend MRI scan to
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confirm the injuries to the ligaments.
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There are some patients that we just recommend MRI scan because
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the patient continues to have cervical spine
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pain and we're trying to explain it.
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And so you will see cervical spine MRI scan even
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in the face of normal cervical spine CT scans.
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Here's a patient where the alignment is normal.
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The anterior alignment line is normal.
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The posterior alignment line is normal.
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The spinolaminar line shows a normal configuration.
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A little bit of distance here is normal.
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But as we get off midline,
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we see that the patient has a fracture, which is
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going from the pedicle into the facet joint.
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In this case, without dislocation and without malalignment.
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So a unilateral facet fracture.
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Here on axial CT scan,
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you see the fractures going through
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both of the facet joints,
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in this case extending to the pedicle central vertebral body
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fracture, as well as the junction between the lamina with the
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transverse process and then extending
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into the medial aspect of the pedicle.
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I want to emphasize that after looking at the fractures,
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make sure you do spend the time to look at the soft tissue
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windows because this is important to demonstrate that
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this patient has an epidural hematoma associated with the
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fractures, displacing the spinal cord
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anteriorly and to the right side.
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This would either need to be evacuated if the patient is
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symptomatic or the cord is being compromised or serial scans,
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usually MRI scan,
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to see whether that this is expanding
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over the course of time.
David M Yousem, MD, MBA
Professor of Radiology, Vice Chairman and Associate Dean
Johns Hopkins University
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