Interactive Transcript
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Hi, it's Dave Yousem again,
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and today we're going to talk on one of my favorite
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topics, which is intradural extramedullary spine.
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I really like this topic very much because in
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general, we're dealing with benign entities.
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So for this talk,
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we're going to be talking about intradural
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extramedullary lesions,
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which are to be distinguished from intradural
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intramedullary and extradural lesions.
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As you can see here in the intradural
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extramedullary category,
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we have lesions that are within the dural sac,
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within the thecal sac,
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but are not within the spinal cord,
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and they are generally characterized
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by what we call is a meniscus sign.
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And that is that there is widening of the
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subarachnoid space above and below
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or on the sides of the mass,
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which is to be distinguished from things
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like the intradural intramedullary tumors,
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which narrow the subarachnoid space,
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and the extradural lesions,
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which also tend to narrow the subarachnoid space.
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So, again, the sine qua non
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of intradural extramedullary lesions is this
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widening of the subarachnoid
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space around the lesion.
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Let's look at the anatomy briefly
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here on these diagrams.
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So with respect to the intradural
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extramedullary cavity,
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we're generally talking about the subarachnoid space
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associated with the spinal cord but not the spinal
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cord itself, which is intradural intramedullary.
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So we're looking extramedullary. When we think
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about the lesions that occur in this space,
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generally, we're talking about the nerve
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roots and the meninges by enlarged.
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But there are sometimes lesions that grow from
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outside the spinal canal into the spinal canal,
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which may be both intradural as well as extradural.
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On this axial section,
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we see the spinal cord and the subarachnoid
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space with the dura surrounding it.
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So lesions can occur
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in that subarachnoid space or
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rise from the dura itself,
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which is part of the thecal sac.
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With respect to our MR imaging techniques,
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we use these standard pulse sequences that we
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would use for almost all spine imaging.
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That is, sagittal T1-weighted scanning,
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sagittal T2-weighted scanning,
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sagittal STIR scanning,
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which is a T2-weighted technique in which there
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is fat suppression, and then we do our axial scans.
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The axial scans in general are based on axial
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T2-weighted scans. However, in the cervical spine,
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we usually use gradient echo scans because it helps
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us to distinguish between disc material versus bone
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in distinguishing between discs and osteophytes.
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For intradural extramedullary lesions,
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we almost always will give gadolinium to better
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characterize the lesions as enhancing
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or non enhancing,
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and also to look at the enhancement pattern.
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The post-gadolinium-enhanced
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scans are done in sagittal and axial plane,
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and when we use the axial plane,
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we're usually applying fat saturation, so that way
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the epidural fat is suppressed as dark against
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the enhancing abnormality. Occasionally,
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we will use diffusion weighted imaging and MRA
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techniques for those lesions that are in
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the intradural extramedullary space.
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