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For the evaluation of intradural intramedullary lesions,

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MRI rules.

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However, there are occasions when we are dealing with

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spondylomyelopathy when the CT scan can be very helpful.

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Here is a case of a classic diagnosis of

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ossification of the posterior longitudinal ligament.

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On the sagittal reconstruction of the axial scans,

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we see this flowing bone which extend from the

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C3 level down to the C7 level,

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which appears to strikingly narrow the spinal canal.

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When we look at it on the axial scans to the right,

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we see just how narrow the spinal canal is,

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and we wonder, how can the spinal cord

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exist in this very narrowed space?

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You notice that the ossification of the

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posterior longitudinal ligament has

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almost a reverse mushroom shape,

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like a mushroom cloud emanating from the back of the bone,

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and it does extend across the disc level.

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So these are not calcified disc.

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This is ossification of the posterior longitudinal ligament.

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Let's just look at it real quickly here on the bone window,

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and you can see that there is a faint

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attachment to the bone of the vertebral body.

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But also there's a component which

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appears to be floating in space,

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as you see on the sagittal scan.

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If we look at the MRI scan in the patient post-op,

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so he's had decompression posteriorly,

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and this is typical of OPLL.

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For OPLL, the surgeons approach the patient posteriorly

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in order to create increased space for the

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spinal cord to float posterior

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and not be compressed by the OPLL.

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But the reason why I wanted to show the MRI

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is just to show the curious nature of this tissue,

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the bone that is spanning across C3,

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C4, C5, C6 to the top of C7.

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And you also see that there is some narrowing

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of the spinal cord.

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Again, spondylomyelopathy cord atrophy,

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or what we call myelomalacia. In this case,

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with dilatation of the subarachnoid space

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because of the decompression.

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And this is demonstrated also on the axial

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scan where we see faint high-signal intensity

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within the spinal cord and dilatation of

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the subarachnoid space, secondary to the

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decompression that's been performed.

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On T1-weighted scans, curiously enough,

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sometimes the OPLL has bone marrow.

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So you may see some bright areas within the OPLL,

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as well as the dark areas of the cortical bone.

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So when it is truly ossified and there is bone marrow,

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you may see fat on T1-weighted scan

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representing the bone marrow within the

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ossification of the posterior longitudinal ligament.

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Here we see the extensive decompression and laminectomy

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that's been performed from C3 down to C7.

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So yet another example of spondylomyelopathy.

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In this case, not due to degenerative disc disease,

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but to ossification of the posterior

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longitudinal ligament with the benefit of the

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CT scan in demonstrating the pathology.