0:01

Let's distinguish neurofibromas from schwannomas.

0:04

Neurofibromas are most commonly seen in the setting

0:06

of neurofibromatosis type 1, and the

0:10

lesions here are generally, again,

0:12

intradural extramedullary neurofibromas.

0:15

You may have intradural intramedullary astrocytomas.

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So with neurofibromatosis type 2,

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the spinal cord lesion is the ependymoma.

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With neurofibromatosis type 1,

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the spinal cord lesion is the astrocytoma.

0:29

We're talking today about intradural extramedullary

0:32

lesion where we're focusing on neurofibromas.

0:35

The signal intensity characteristics and enhancement

0:38

characteristics of neurofibromas cannot readily

0:41

be distinguishable from schwannomas. However,

0:45

there is this well-reported so-called target sign,

0:49

which may suggest a neurofibroma over

0:52

a schwannoma. With the target sign,

0:55

you see central low signal intensity

0:57

within the nerve sheath tumor,

1:00

surrounded by brighter signal intensity,

1:02

and that is what is referred to as the target sign.

1:06

In addition,

1:07

neurofibromas are less likely to have cystic

1:10

degeneration than schwannomas. Neurofibromas are,

1:14

however, more likely to have malignant degeneration,

1:18

particularly in the setting of a plexiform

1:22

neurofibroma and neurofibromatosis type 1.

1:25

With neurofibromatosis and a plexiform, or malignant

1:29

degeneration of a plexiform neurofibroma, or

1:32

malignant peripheral nerve sheath tumor, one may see

1:35

more aggressive growth pattern with

1:38

bone destruction and erosion.

1:39

This is a patient who has neurofibromatosis type 1,

1:42

and we see that there are multiple lesions in the

1:45

lumbar region. Let's look at this axial scan.

1:49

And as we look at it, for example,

1:51

if we were to put a parasagittal

1:54

section through here,

1:56

what we would find is a darker signal intensity centrally,

2:00

and a brighter signal intensity in the periphery.

2:04

This is our so-called target sign.

2:06

So if I were to do it in cross section,

2:08

you'd see the darker area here

2:12

and the brighter area here,

2:15

and this makes that target sign

2:17

of neurofibromatosis type 1.

2:19

You can see that this would also be what

2:21

you would see on the left side, as well.

2:24

So these are extradural lesions that I'm

2:28

demonstrating on the axial scans.

2:30

However, clearly on the sagittal scan,

2:33

the patient had additional lesions that

2:35

are intradural extramedullary.

2:38

Here's the end of the spinal cord.

2:40

So these are the referral to the target sign of

2:43

neurofibromatosis type 1 of a neurofibroma

2:46

of neurofibromatosis type 1.

2:48

These are parasagittal images,

2:50

and you see that we have multiple

2:52

sort of concentric rings,

2:54

some of which show a lower signal intensity

2:56

centrally and a brighter signal

2:58

intensity in the periphery,

3:00

so-called target sign of neurofibroma.

3:03

The characteristic features of neurofibromatosis

3:05

type 1 affecting the spinal cord are the

3:09

neurofibromas or nerve sheath tumors.

3:11

However, one might also see dural ectasias,

3:14

as well as arachnoid cysts.

3:16

Scalloping of the vertebral body is also

3:19

another finding that is associated with

3:21

neurofibromatosis type 1, and is effectively

3:24

another type of dural ectasia. Lateral meningoceles,

3:28

generally occurring in the thoracic region, are

3:31

also a feature of neurofibromatosis type 1.

3:34

These patients may also show kyphoscoliosis

3:37

and occasionally lumbar meningoceles.