Interactive Transcript
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In addition to the evaluation of the stability of the ligaments
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with atlanto-occipital and atlanto-axial dissociation,
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we obviously want to look at the vertebral bodies themselves.
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This is an example of a Jefferson fracture.
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It's a comminuted fracture,
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actually a burst fracture of the C1 vertebra.
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Sometimes it will just affect the anterior
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arches of the C1 vertebra.
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Sometimes it also affects the posterior arch
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of the C1 vertebra.
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As you can see here,
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we have the right sided posterior arch,
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which is somewhat comminuted,
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as well as the anterior arch of C1.
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Now, this in and of itself, does not necessarily mean it's
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an unstable fracture. If the ligaments are intact,
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it actually may represent a stable fracture.
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These fractures are also nicely demonstrated
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on the coronal reconstruction,
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where we can see the fracture fragment on the left
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side, as well as the comminuted
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fracture fragment on the right side.
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And as we proceed a little bit more posteriorly,
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you can see the additional line of fracture.
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Let's look at this on the sagittal scan.
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And we want to look and make sure that
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the lentilodontoid distance is preserved.
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And this looks perfectly fine, nicely at pose
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there. You can see a fracture fragment on the
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superior arch of the anterior arch of C1.
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Here is the fracture going through both anteriorly
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as well as in the posterior arch,
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representing this somewhat comminuted burst fracture.
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Looks like it's a little bit worse on
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the right side than the left side.
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The orientation of the fracture fragments
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on the coronal image is very important.
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What you see is that there is offset of the lateral mass of
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C1 from the lateral mass of C2 on both sides.
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So this should normally be aligned.
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This is all part of that same mechanism of
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burst where it kind of explodes outward.
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And so these lateral masses are laterally displaced
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in this type of fracture, the Jefferson fracture.
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On the CT scan of the Jefferson fracture,
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we saw that the lateral mass of C1 was displaced laterally
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on both sides compared to the lateral
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mass of the odontoid process.
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That suggests that there probably is ligamentous injury.
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Let's look at the MRI scan on the same patient.
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So this is the T2-weighted scan.
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Here's the STIR images.
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We've talked about how the STIR image is the best
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sequence for looking at ligamentous injury.
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So we will follow the anterior longitudinal ligament upward
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and we see that there does appear to be an intact anterior
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longitudinal ligament as we go up to the clivus.
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There is some prevertebral edema as this bright signal intensity.
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As we follow the posterior longitudinal ligament, we notice
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that we have this disruption of the posterior longitudinal
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ligament as it converts to the tectorial membrane.
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And there we have a discontinuity here.
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So there is ligamentous disruption
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of the tectorial membrane.
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As we go off midline, we see the atlanto-occipital region, on this
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side shows normal distance and just
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very slight high signal intensity.
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The atlantoaxial space is also normal with
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just a little bit of bright signal intensity.
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As we go off posteriorly towards where the fracture has occurred,
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we do see bright signal intensity edema
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in the adjacent soft tissues.
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But note that when we go to the contralateral side, we see
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something different. Here we have brighter signal intensity.
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It's narrower anterior than posteriorly.
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So this kind of triangular look implies that there is
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ligamentous injury extending along the posterior
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margin of the atlantoaxial space,
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and that is asymmetric from the right side to the left side,
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where you see that there's the same distance between the two.
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So there is this little offset.
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And there is likely this ligamentous injury as well as
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the injury that we described to the tectorial membrane.
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We want to look at the spinal laminar line
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and the spinal laminar ligaments,
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which effectively are the ligamentum flavum.
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They look just fine. And there isn't really offset here.
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The atlanto-odontoid space is preserved.
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If we look at the axial scans,
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we will see that bright signal intensity here
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which is largely in the retropharyngeal space,
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more so than the prevertebral space.
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There is a little bit of bright signal intensity
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in the prevertebral space,
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but this is anterior to the longus musculature.
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So here's our longus musculature.
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This is actually in the retropharyngeal space
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rather than the prevertebral space.
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On this MRI scan,
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I want you to pay attention to the flow
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voids of the vertebral arteries.
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Notice that the left vertebral artery shows a normal flow void,
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but the right vertebral artery has
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high signal intensity within it.
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This implies that there may be dissection or thrombosis of the
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right vertebral artery that is associated with the fracture,
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which, as you recall,
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was more on the right side than the left side on the CT scan.
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So there has been compromise of the
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right vertebral artery versus the left vertebral artery.
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