0:00

Another of the intrinsic lesions of the

0:03

optic nerve is the optic nerve glioma.

0:06

This is a tumor which is seen in the pediatric

0:09

population largely, secondary to neurofibromatosis type 1.

0:14

Here we have a patient who has enlargement of the optic nerve

0:17

within the optic nerve sheath,

0:19

demonstrated on the T2-weighted imaging.

0:23

We separate the optic nerve enlargement

0:26

from the sheath on the T2-weighted scan.

0:31

So, here is the optic nerve enlargement,

0:34

separate from the optic nerve sheath.

0:38

This second case, we see that the patient has the

0:42

bilateral involvement of the optic nerves,

0:44

and we are starting to see thickening of the optic chiasm, as well.

0:50

On the FLAIR image,

0:51

we see that the chiasm is markedly enlarged and

0:54

the tumor is going into the optic radiations,

0:59

the temporal lobe optic radiations. And from there,

1:03

could extend even to the occipital lobes.

1:06

This is a low-grade astrocytoma, pilocytic astrocytoma,

1:11

associated with neurofibromatosis type 1.

1:14

In general, this is very difficult to treat,

1:16

and therefore, it is merely observed rather than addressing surgically.

1:23

Here's a patient with a CT scan, demonstrating marked

1:28

enlargement of the optic nerve sheath complex

1:31

in a patient who had optic nerve glioma.

1:35

One of the features of neurofibromatosis is something

1:39

that we hear about a lot but never show on imaging.

1:45

This is an image of Lisch nodules.

1:47

These are these brown pigmentation on the iris of the globe.

1:54

And this is one of the primary criteria

1:57

of neurofibromatosis type 2.

2:00

There are no imaging features on CT or MRI

2:04

scan that correlate with Lisch nodules.

2:06

Remember also that Café-au-lait spots and axillary

2:09

freckling also constitute some of the major criteria

2:13

of neurofibromatosis type 1,

2:15

as well as plexiform neurofibromas.

2:20

So the primary criteria for neurofibromatosis include

2:23

six or more café au lait spots, two or more Lisch nodules,

2:27

axillary freckling, an optic pathway glioma,

2:31

first-degree relative with neurofibromatosis,

2:33

a plexiform neurofibroma or bone dysplasia.

2:38

Now, that bone dysplasia often affects the greater wing of

2:42

the sphenoid, and therefore can lead to proptosis as you

2:49

have herniation of brain tissue through the greater ring

2:51

of the sphenoid, or what is characteristic of neurofibromatosis,

2:55

which is pulsatile exophthalmos,

2:58

that is, that CSF pulsation in the brain is transmitted to the orbit

3:02

and the globe is seen to pulse in and cause exophthalmos.

3:08

Within the orbit itself,

3:10

not only do we have the possibility of bony

3:13

dysplasias and optic nerve gliomas,

3:15

you may have a plexiform neurofibroma of the fifth

3:18

cranial nerve that can infiltrate the orbit.

3:22

You can have remodeling of the walls of the orbit.

3:26

You can have expanded CSF space into the orbit,

3:30

enlarged foramina of the orbit from neurofibromas

3:33

of the cranial nerves,

3:34

and you may have elongation of the globe itself,

3:38

one of the causes of macrophthalmia, so-called buphthalmos.