Interactive Transcript
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Well, if you've watched any of the Dave Yousem presentations,
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you know I like mnemonics.
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And my favorite mnemonic
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for describing pathology in the central
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nervous system is VITAMIN C and D.
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This refers to vascular, infectious, traumatic,
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acquired, metabolic, idiopathic, neoplastic,
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congenital and drugs. With respect to
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the intradural extramedullary space,
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neoplasms are going to be the predominant abnormality,
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followed by some of the congenital and
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infectious and vascular lesions.
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But we're going to focus mostly on the neoplastic
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category. Fortunately, as I said,
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this is a happy zone,
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because most of the lesions in the neoplastic
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category are benign lesions, and of these,
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schwannomas and meningiomas tend to predominate.
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So here are the intradural extramedullary neoplastic category lesions,
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and they are the nerve sheath tumors.
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So, in general,
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a generic term would be nerve sheath tumors.
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And within that, we would have schwannomas
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and neurofibromas, and potentially even
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plexiform neurofibromas, or malignant peripheral nerve
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sheath tumors. Of the nerve sheath tumors,
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schwannomas are more common than neurofibromas.
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The other neoplasms in the intradural extramedullary
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space are predominated by benign conditions.
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So we have our nerve sheath tumors.
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Our next most common is going to be a meningioma,
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obviously occurring in the dura of the thecal sac.
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And then the other benign tumors
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would be a paraganglioma.
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And down in the filum terminale region,
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we have ependymomas. They may say ependymomas?
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I thought we discussed those in the intradural
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extramedullary compartment.
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And that is true, that when they occur in the spinal
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cord, they are obviously intramedullary lesions,
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but the filum terminale is not considered
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part of the spinal cord.
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It's considered a fibrous tissue at the end of
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the spinal cord, beyond the spinal cord.
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And so, tThese are usually characterized as intradural
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extramedullary lesions, and they are usually low
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grade neoplasms or relatively benign.
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The one neoplasm that is malignant that we have
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to worry about is subarachnoid seeding,
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and this is usually from a CNS primary tumor,
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generally in the brain that is shedding cells into the
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subarachnoid space and infiltrating the spinal canal.
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Of the nerve sheath tumors,
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the most common are going to be schwannomas.
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And these nerve sheath tumors are most commonly
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intradural extramedullary. However,
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sometimes you will find them in the extradural
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compartment and sometimes you will find them spanning
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intradural and extradural, so-called dumbbell lesions,
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which have a component that is still within the thecal sac
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and a different component that is outside the thecal sac.
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So these are our nerve sheath tumors.
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