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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,

0:19

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

0:29

infectious and vascular lesions.

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But we're going to focus mostly on the neoplastic

0:34

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.

0:58

And within that, we would have schwannomas

1:01

and neurofibromas, and potentially even

1:03

plexiform neurofibromas, or malignant peripheral nerve

1:07

sheath tumors. Of the nerve sheath tumors,

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schwannomas are more common than neurofibromas.

1:12

The other neoplasms in the intradural extramedullary

1:15

space are predominated by benign conditions.

1:19

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.

1:28

And then the other benign tumors

1:29

would be a paraganglioma.

1:31

And down in the filum terminale region,

1:34

we have ependymomas. They may say ependymomas?

1:37

I thought we discussed those in the intradural

1:41

extramedullary compartment.

1:43

And that is true, that when they occur in the spinal

1:46

cord, they are obviously intramedullary lesions,

1:49

but the filum terminale is not considered

1:51

part of the spinal cord.

1:53

It's considered a fibrous tissue at the end of

1:56

the spinal cord, beyond the spinal cord.

1:59

And so, tThese are usually characterized as intradural

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extramedullary lesions, and they are usually low

2:05

grade neoplasms or relatively benign.

2:09

The one neoplasm that is malignant that we have

2:12

to worry about is subarachnoid seeding,

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and this is usually from a CNS primary tumor,

2:18

generally in the brain that is shedding cells into the

2:22

subarachnoid space and infiltrating the spinal canal.

2:27

Of the nerve sheath tumors,

2:28

the most common are going to be schwannomas.

2:32

And these nerve sheath tumors are most commonly

2:36

intradural extramedullary. However,

2:38

sometimes you will find them in the extradural

2:41

compartment and sometimes you will find them spanning

2:44

intradural and extradural, so-called dumbbell lesions,

2:48

which have a component that is still within the thecal sac

2:51

and a different component that is outside the thecal sac.

2:54

So these are our nerve sheath tumors.