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One of the other entities that may lead

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to spinal stenosis that is relatively

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specific to the cervical spine is

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something called ossification of the

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posterior longitudinal ligament or OPLL.

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We usually use the term OPLL.

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What it represents is, just as you...

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as you...

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as the terms used...

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imply,

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and that is that there is ossification

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that is seen posterior to the vertebral

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bodies in the posterior

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longitudinal ligament.

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And this ossification can vary in its thickness.

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So if we look on the axial scans,

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you see just how thick on the left side

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the ossification of the posterior

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longitudinal ligament is compared

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to the right side,

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where it is somewhat abbreviated,

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in an anterior-posterior dimension much shorter.

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So this is a process which can really

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severely narrow the spinal canal.

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As you can see,

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there's two different cases. Here on the

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left, it extends from the C1-C2 level

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all the way down to the

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C5-C6 level. On this case,

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we have C2, C3, C4, C5, C6,

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it's going all the way down to the C7 level

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in a pretty much contiguous

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fashion along the posterior aspect of the

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vertebral bodies. By enlarged

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OPLL need not be associated with disc

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disease. So, in point of fact,

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on the case to the left,

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when you look at the sagittal scan,

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there really isn't that much narrowing

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of the disc spaces to suggest the degenerative

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change on the case to the left.

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On the case to the right,

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you see C2-C3, C3-C4 have pretty good looking

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discs as far as the superior

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inferior height. However,

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there is some narrowing from

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C4 down to C7.

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The other thing that you see on the

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case to the left...

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I'm sorry,

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to the right, is the presence of flowing

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osteophytes that extend from the C3

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level down to the T1-T2 level.

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This is a phenomenon that is associated

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with OPLL and that is DISH.

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DISH refers to diffuse idiopathic

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skeletal hyperostosis.

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It typically is manifest by flowing

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osteophytes along the anterior, the

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anterior to the spinal canal.

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Usually, again, not associated with degenerative

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disc disease, but with a separate process

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known as DISH.

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So DISH and OPLL occur together quite

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frequently. When you have DISH and OPLL,

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the other phenomenon that you can see is

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ossification or calcification of the

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ligamentum flavum. So remember,

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the ligamentum flavum is the

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ligament's posteriorly.

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So when you combine the OPLL

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with ligamentum flavum,

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ossification or calcification,

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you can get a very narrow canal.

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The problem with this is that in the cervical spine,

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that often leads to spinal cord

3:19

compression and myelopathy.

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As you can imagine,

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OPLL is difficult to identify on the MRI

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scan because it's dark in signal intensity.

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It looks effectively like bone.

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So here we have on the sagittal scans,

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a narrowed canal,

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but the presence of the OPLL is

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not as clearly identified.

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Where it actually is,

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is here's the back of the vertebral bodies.

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And what you're seeing here is all of

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the OPLL that was evident on the CT

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scan. In fact, this case is the

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MRI that accompanied the CT scan on

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the previous slide. On axial scans,

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remember that on your

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gradient echo scan,

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bone and ossification is going to be

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dark on the gradient echo scan.

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So on this axial GRE scan,

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what you see is dark signal intensity

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representing the ossification of the

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posterior longitudinal ligament.

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Here we have ossification,

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which is occurring actually in the

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thoracic spine from posteriorly.

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The patient has an incidental hemangioma

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or venous vascular malformation

4:44

of the vertebral body.

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We have the spinal cord coming down,

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and then the spinal cord is displaced

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anteriorly with abnormal signal

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intensity within the spinal cord

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at the mid thoracic levels.

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What's the etiology? In this case,

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this dark signal intensity is

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ossification of the ligamentum flavum.

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As I mentioned,

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this may occur in association with OPLL

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and DISH, or it may occur independently.

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This is another source of spinal stenosis.