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Hi, it's Dave Yousem from Johns Hopkins University

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School of Medicine. Here to talk to you today

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about intradural intramedullary spinal lesions.

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Classically, when we think about spinal lesions,

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we separate them into three different

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categories, intradural intramedullary lesions,

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intradural extramedullary lesions, and extradural lesions.

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The extradural lesions, by and large,

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are most commonly secondary to degenerative

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disease and this includes degenerative disc disease

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and osteophytes and ligamentum flavum thickening,

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as well as facet joint disease.

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These are lesions which compress the spinal

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cord and the CSF from outside the thecal sac.

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Contrast that with the intradural diseases.

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These are diseases that compress the

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cord within the thecal sac.

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However, the extramedullary lesions are ones that are

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outside the spinal cord, demonstrated here,

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whereas the intradural intramedullary lesions are

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the lesions that are intrinsic to the spinal cord.

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Now, you note a couple of things.

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The CSF space with intradural extramedullary lesions,

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shows widening at the margins of the lesion.

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So we look for CSF space widening on our T2-weighted scan

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where the CSF is bright.

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With intradural intramedullary lesion,

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you see that the CSF space narrows at the site

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of the primary lesion both above and below

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the lesion or from side to side.

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This is sometimes difficult to distinguish

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from extradural disease, which also causes narrowing.

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But you see that that narrowing is more

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eccentric when you have a lesion that

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is in the extradural space.

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So these features allow us to separate the

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lesions of the spine into separate

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differential diagnoses because intramedullary

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lesions are different in their histology from

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extramedullary lesions and extradural lesions.

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With respect to the intradural intramedullary lesions,

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we're talking about spinal cord lesions.

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And it's important to recognize that the

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spinal cord is separated into the cervical

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region and the thoracic region.

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But by and large, the end of the spinal cord, what we call the

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conus medullaris, ends at approximately the

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L1-level. It may extend to the L1-L2 terminus region here,

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but it's usually above the L2 level.

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The portion of the intramedullary space that persists below

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the L2 level is called the filum terminale.

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However, lesions of the filum,

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although that's the extension of the spinal cord,

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are considered intradural, but extramedullary lesions.

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The anatomy of the spinal cord is somewhat complex.

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Here we see a nice diagram describing the

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various tracts that course through

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the spinal cord. In this diagram,

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the pinkish ones are the ascending tracts,

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predominantly sensory tracts,

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whereas the descending tracts

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are the motor tracts .

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The largest of these will be demonstrated in just a moment.

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What we also note is that the cord gray matter

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is central in location and this is verified on

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the histologic section that is demonstrated to

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the right, with the central gray matter being yellowish

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and the white matter tracts being the more blue color.

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To simplify things for you,

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we think about the main tracts that are in the

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spinal cord, and those are the motor tracts of

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the anterior corticospinal tract and the

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lateral corticospinal tract, and the anterior

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part of the spinal cord, and the lateral

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part of the spinal cord, clearly.

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And then, we have the lateral spinothalamic tract,

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which is largely pain and temperature sensation,

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and the dorsal columns, which are the vibratory

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and position sentence.

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In this diagram, again, you see the central gray matter.

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To identify these components of the spinal cord,

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I think that the gradient echo scans

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in the cervical spine are the best.

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So here we have the histologic drawing.

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Here we have the diagram of the gray matter.

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And as you can see, within the spinal cord,

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there is that type of structure that

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looks like the gray matter

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outlined on the gradient echo scan

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as the brighter areas centrally.

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And then, we also are able to separate the

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spinal cord into the lateral areas with

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the lateral corticospinal tract

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in the spinothalamic tract,

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the posterior column area in the center,

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paramedian region posteriorly,

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and then the anterior corticospinal tracts, as well.

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The importance of this anatomy is that there

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are different syndromes that are associated

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with cord lesions associated with the various tracts.

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So we think of the Brown-Séquard syndrome,

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which is a hemicord lesion which leads to

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ipsilateral sensory and contralateral pain and temperature,

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sensory deficits, as well as ipsilateral motor paralysis because

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of the anterior corticospinal tract and the

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spinothalamic tracts being involved.

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We have the anterior cord syndrome,

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which is usually associated with cord strokes

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and this can cause bilateral pain and

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temperature involvement because of the lateral

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spinothalamic tracts involved,

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as well as the anterior corticospinal

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tract being involved bilaterally.

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And then, we have the central cord syndrome.

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The central cord syndrome is typically what we

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see with degenerative spondylomyelopathy,

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and this will affect the upper motor extremities

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more than the lower motor extremities because

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of the central nature of it, as well as having some motor effect

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because of the central gray matter being involved.