0:00

This was an elderly gentleman who had bilateral visual loss.

0:05

Let's start with looking at the magnified

0:07

views of the optic nerves.

0:09

These are fat-suppressed T2-weighted imaging, and we

0:13

see very nicely the optic nerve sheath

0:16

and the optic nerve intraorbitally.

0:21

Here we are seeing the globes,

0:23

and now we come to the optic nerves.

0:26

And at first blush,

0:27

the optic nerves and the optic nerve sheath look good,

0:30

demonstrating the dark signal intensity of the optic nerve

0:34

contrasted by the bright signal intensity

0:36

of the CSF within the optic nerve sheath.

0:40

Remember, as I said previously, the optic nerve,

0:42

because it is a portion of the white matter of the brain

0:46

should have similar signal intensity to the white matter

0:49

elsewhere in the brain. And these look normal initially.

0:53

However, as we scroll more posteriorly,

0:55

we're going to find some abnormality.

1:00

We are at the level of the optic canal.

1:04

How do we know we're at the level of the optic canal?

1:07

Once again,

1:08

we identify the dark signal intensity of the anterior

1:11

clinoid process, and we note that the optic canal is going

1:14

to be medial to the anterior clinoid process.

1:19

Here we see the optic nerve,

1:22

and we note that the signal intensity has changed.

1:24

It is no longer the same as the white matter of the brain.

1:29

It is brighter than the white matter and seems as if it's bilateral.

1:33

So we would consider, once again,

1:35

could this patient have neuromyelitis,

1:37

optica or another cause of bilateral optic neuritis?

1:42

We're going to continue to scroll a little bit more

1:45

posteriorly, and we continue to see the bright signal

1:49

intensity of both optic nerves

1:51

as they come intracranially.

1:54

And now, we're within the brain substance and in the

1:57

subarachnoid space, and we're coming to the optic chiasm,

1:59

which has normal signal intensity.

2:02

The next thing to do is to look at the

2:03

postgadolinium-enhanced images.

2:08

These are magnified views of the postgadolinium fat

2:11

suppressed images of the optic nerves and the orbits.

2:15

And what one sees is somewhat fluffier enhancement

2:21

around the optic nerve sheath, potentially better seen

2:24

on the left side than the right side on this image.

2:27

So, what I'm describing is the abnormal contrast

2:31

enhancement that seems to be beyond the normal thin

2:36

enhancement of the optic nerve sheath, on the left side,

2:40

and it looks as if it's going into the intraorbital fat.

2:43

Let's see if that persists as we scroll more posteriorly.

2:47

On this image as well,

2:50

we see that the enhancement of the optic nerve sheath

2:54

seems somewhat ragged in appearance and is a little

2:56

more prominent than what I've demonstrated in the

3:00

normal optic nerve sheath previously,

3:01

but it's not as thick as one would expect

3:03

for an optic nerve sheath meningioma.

3:06

So right now, we have abnormal signal in the optic nerves,

3:10

as well as fluffy enhancement around the optic nerve sheath.

3:15

On this image, we are at the level of the optic canal.

3:20

How do we know we're in the optic canal?

3:22

We identify the anterior clinoid process.

3:27

So, the anterior clinoid process has

3:30

its bone marrow signal and cortical signal,

3:33

seen as the dark and bright signal intensity here.

3:36

And we are identifying the optic nerve as showing

3:39

contrast enhancement bilaterally.

3:46

In this case,

3:48

we also start to see some abnormalities associated

3:51

with the intracranial compartment.

3:54

For example,

3:55

we note that there does appear to be some enhancement

3:58

along the frontal horns of the lateral ventricles.

4:00

So, let's shift at this point to the contrast

4:03

enhanced images of the brain.

4:07

This is a standard post-gadolinium non-fat

4:10

suppressed image of the brain.

4:12

So you note that the orbital fat remains bright.

4:15

And as we scroll through the brain,

4:18

we come to the more superior aspect of the brain,

4:21

and we note abnormal enhancement in the

4:25

subarachnoid space of the brain.

4:30

This is a bilateral process

4:34

with abnormal enhancement in the subarachnoid space,

4:39

looking as linear areas deep to the sulci of the brain.

4:46

And this goes to the superior aspect of the brain, as well.

4:51

So, how do we wrap this all together?

4:54

So, this is an instance where we might suggest that

4:57

there is a process of the subarachnoid space,

5:01

either infectious inflammatory or neoplastic,

5:05

that could be affecting the optic nerve sheath

5:08

complex and affecting the optic nerve, secondarily.

5:12

In my report on this case,

5:14

I recommended evaluation of the cerebrospinal

5:17

fluid by lumbar puncture.

5:20

This patient ended up with a final diagnosis of leukemia

5:24

with subarachnoid space involvement of the leukemia,

5:27

as well as the optic nerve sheath complex,

5:30

leading to bilateral optic neuritis.