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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.