Interactive Transcript
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Let's drill down on the nerve sheath tumors which
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are the most common lesions of the intradural
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extramedullary neoplastic category.
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So what we have here are schwannomas
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and neurofibromas,
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predominantly, and rarely you will have malignant
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degeneration which occurs more commonly in
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neurofibromatosis and neurofibromas than schwannomas.
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And within the neurofibromatosis,
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this is more common with neurofibromatosis type 1
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to have malignant degeneration.
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Schwannomas are more common.
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They occur both sporadically and in association
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with neurofibromatosis type 2.
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Neurofibromas are the sine qua non
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of neurofibromatosis type 1.
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Here is a stereotypical lesion of the intradural
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extramedullary compartment.
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You will note that at the edge of the tumor
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we have what's called meniscus sign.
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And the meniscus sign is where the CSF will widen at
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the border with the lesion, as
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opposed to narrowing it.
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Remember that narrowing of the subarachnoid space
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occurs in intradural intramedullary lesions
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and extradural lesions.
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But the one where the CSF space is, if anything
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widened, is going to be the intradural
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extramedullary.
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This is a lesion that is occurring in the cervical
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spine and is displacing the spinal cord anteriorly,
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as you see here. In the cervical
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spine and in the lumbar spine,
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schwannnomas are more common than meningiomas.
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In the thoracic spine, meningiomas are more common.
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Let's look at the lesion down below here.
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Here we have a patient in the center where
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the lesion is in the lumbar zone.
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You'll notice that the spinal cord has terminated
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here, the so-called conus medullaris.
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So we are clearly intradural but extramedullary.
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It's outside the spinal cord.
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On the T2-weighted scan to the right,
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you'll see that it is associated with the nerve roots
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of the cauda equina below the level of the spinal
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cord and it has both a cystic portion,
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as well as a solid portion.
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And this is not uncommon with schwannomas to
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have cystic degeneration of the tumor.
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Again, in the lumbar region,
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schwannomas are more common than meningiomas.
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Here's a different lesion.
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So here we are again in the lumbar zone and we have
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a patient who has a low signal intensity
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lesion on T one way it scans,
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it's bright on T two weighted scan in the center.
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And on the right hand image,
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you'll see that it solidly enhances.
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Just want to point out one thing,
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and that is that even though this lesion is very
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bright on the T2-weighted scan, almost
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the same as cerebrospinal fluid,
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you'll notice that it actually is a solid lesion
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in that it's showing uniform homogeneous enhancement.
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So here, although the lesion in T2-weighted scan is very bright,
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it shows solid enhancement on the sagittal and axial
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post-gadolinium enhanced scan. In the lumbar region,
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solid mass.
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We're going to suggest that this is indeed
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a Schwannoma. Could it be a meningioma?
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It does have a border with the dura,
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but it does not have a dural tail,
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which is that enhancement that occurs
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at the borders of the lesion,
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which extends beyond the attachment with the dura.
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No dural tail, favoring schwannoma.
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As I mentioned,
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schwannomas may occasionally occur both intradurally,
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as well as extradurally. Here is such a case.
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On the axial scans,
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we see a mass that is within the neural foramen,
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as well as within the thecal sac.
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This is probably the best image to show that. We have
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the component that is within the thecal sac,
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and we have the component which is extending into
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the neural foramen, which is extradural.
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And this part is intradural.
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You'll notice that the lesion is not within the spinal
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cord, so it's intradural but extramedullary.
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And we have the so-called meniscus sign,
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as I demonstrated here and here.
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This lesion is intradural, extradural,
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and so-called dumbbell shaped lesion that can occur
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with Schwanomas or neurofibromas. In this case,
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it was a cervical spine dumbbell Schwannoma.
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