0:00

We are continuing our analysis of

0:02

intraconal lesions of the orbit.

0:06

This next patient presented with left-sided visual loss.

0:11

As we look at the T1 and T2 weighted

0:13

scans of the brain MRI,

0:17

we notice an asymmetry in the size of the left optic

0:22

nerve compared with the right optic nerve.

0:26

We see that the left optic nerve caliber

0:30

is wider than the right optic nerve.

0:35

This is true both on the T2-weighted scan

0:38

as well as the T1-weighted scan.

0:40

We also note that the normal signal intensity of the

0:43

optic nerve, which should look like white matter,

0:46

is brighter

0:48

on the T2-weighted scan.

0:51

With respect to optic nerve sheath lesions,

0:55

we want to make the distinction between that,

0:58

which is respecting the optic nerve versus the meninges

1:01

that surround the optic nerve sheath.

1:03

Because the differential diagnosis is an optic nerve glioma

1:08

versus an optic nerve meningioma.

1:10

Remember that the optic nerve is not a peripheral nerve.

1:14

It's actually a portion of white matter from the brain,

1:17

and therefore,

1:17

we do not get schwannomas of the optic nerve.

1:21

We get optic nerve gliomas or astrocytomas,

1:24

and the vast majority of these

1:26

are pilocytic astrocytomas.

1:29

The tumor of the optic nerve sheath is a meningioma

1:33

and this will generally spare the signal

1:35

intensity of the optic nerve.

1:38

Let's look at the additional sequences on this patient.

1:42

As we scroll further inferiorly,

1:45

we note that there is a large mass

1:48

along the right side of the neck.

1:50

This mass is quite heterogeneous and infiltrates

1:54

a great portion of the right side of the neck.

1:57

We identify the internal carotid artery.

2:01

And we identify the vertebral artery,

2:03

and we see how closely opposed the tumor is to these blood vessels.

2:09

This is a multiloculated lesion in the right side of the neck.

2:14

If we scroll further inferiorly,

2:17

we see that it will continue down the neck,

2:21

extending to the subcutaneous tissue,

2:23

as well as infiltrating the fat,

2:25

as well as infiltrating the musculature,

2:28

while it also infiltrates the carotid sheath.

2:35

For those with good

2:38

analytical tools,

2:40

one might also note that the neuroforamen on the right side,

2:44

at this cervical spine level, is enlarged.

2:51

Further inferiorly,

2:52

we note that there is an additional lesion that is

2:55

infiltrating around the clavicle

2:58

and between the clavicles.

3:00

And an additional lesion in the right axilla.

3:05

This is a patient who has neurofibromatosis type 1 with

3:09

plexiform neurofibromas, affecting the right side of the neck,

3:13

as well as the anterior chest wall and the right axilla.

3:18

Now, when we consider the lesion in the orbit,

3:21

it makes a lot more sense.

3:23

This is a patient who has an optic nerve glioma as

3:26

part of the neurofibromatosis type 1 spectrum.

3:30

There are seven major criteria for neurofibromatosis type 1.

3:36

They include café-au-lait spots,

3:38

axillary freckling, lisch nodules,

3:42

plexiform neurofibromas, optic nerve pathway gliomas,

3:47

a family history of neurofibromatosis,

3:51

and bony dysplasia.