0:01

Let's drill down on the nerve sheath tumors which

0:03

are the most common lesions of the intradural

0:07

extramedullary neoplastic category.

0:09

So what we have here are schwannomas

0:12

and neurofibromas,

0:13

predominantly, and rarely you will have malignant

0:16

degeneration which occurs more commonly in

0:19

neurofibromatosis and neurofibromas than schwannomas.

0:24

And within the neurofibromatosis,

0:25

this is more common with neurofibromatosis type 1

0:29

to have malignant degeneration.

0:31

Schwannomas are more common.

0:33

They occur both sporadically and in association

0:36

with neurofibromatosis type 2.

0:39

Neurofibromas are the sine qua non

0:42

of neurofibromatosis type 1.

0:44

Here is a stereotypical lesion of the intradural

0:49

extramedullary compartment.

0:51

You will note that at the edge of the tumor

0:53

we have what's called meniscus sign.

0:56

And the meniscus sign is where the CSF will widen at

1:01

the border with the lesion, as

1:03

opposed to narrowing it.

1:05

Remember that narrowing of the subarachnoid space

1:09

occurs in intradural intramedullary lesions

1:12

and extradural lesions.

1:13

But the one where the CSF space is, if anything

1:16

widened, is going to be the intradural

1:20

extramedullary.

1:21

This is a lesion that is occurring in the cervical

1:24

spine and is displacing the spinal cord anteriorly,

1:28

as you see here. In the cervical

1:30

spine and in the lumbar spine,

1:33

schwannnomas are more common than meningiomas.

1:37

In the thoracic spine, meningiomas are more common.

1:40

Let's look at the lesion down below here.

1:43

Here we have a patient in the center where

1:46

the lesion is in the lumbar zone.

1:49

You'll notice that the spinal cord has terminated

1:51

here, the so-called conus medullaris.

1:53

So we are clearly intradural but extramedullary.

1:57

It's outside the spinal cord.

1:59

On the T2-weighted scan to the right,

2:01

you'll see that it is associated with the nerve roots

2:04

of the cauda equina below the level of the spinal

2:07

cord and it has both a cystic portion,

2:10

as well as a solid portion.

2:12

And this is not uncommon with schwannomas to

2:14

have cystic degeneration of the tumor.

2:17

Again, in the lumbar region,

2:20

schwannomas are more common than meningiomas.

2:23

Here's a different lesion.

2:24

So here we are again in the lumbar zone and we have

2:28

a patient who has a low signal intensity

2:32

lesion on T one way it scans,

2:34

it's bright on T two weighted scan in the center.

2:38

And on the right hand image,

2:39

you'll see that it solidly enhances.

2:41

Just want to point out one thing,

2:43

and that is that even though this lesion is very

2:45

bright on the T2-weighted scan, almost

2:48

the same as cerebrospinal fluid,

2:50

you'll notice that it actually is a solid lesion

2:53

in that it's showing uniform homogeneous enhancement.

2:56

So here, although the lesion in T2-weighted scan is very bright,

3:01

it shows solid enhancement on the sagittal and axial

3:05

post-gadolinium enhanced scan. In the lumbar region,

3:09

solid mass.

3:11

We're going to suggest that this is indeed

3:13

a Schwannoma. Could it be a meningioma?

3:16

It does have a border with the dura,

3:18

but it does not have a dural tail,

3:20

which is that enhancement that occurs

3:23

at the borders of the lesion,

3:25

which extends beyond the attachment with the dura.

3:28

No dural tail, favoring schwannoma.

3:32

As I mentioned,

3:33

schwannomas may occasionally occur both intradurally,

3:37

as well as extradurally. Here is such a case.

3:40

On the axial scans,

3:43

we see a mass that is within the neural foramen,

3:47

as well as within the thecal sac.

3:50

This is probably the best image to show that. We have

3:53

the component that is within the thecal sac,

3:55

and we have the component which is extending into

3:58

the neural foramen, which is extradural.

4:01

And this part is intradural.

4:03

You'll notice that the lesion is not within the spinal

4:06

cord, so it's intradural but extramedullary.

4:09

And we have the so-called meniscus sign,

4:11

as I demonstrated here and here.

4:15

This lesion is intradural, extradural,

4:18

and so-called dumbbell shaped lesion that can occur

4:22

with Schwanomas or neurofibromas. In this case,

4:25

it was a cervical spine dumbbell Schwannoma.