0:00

Yeah, so the first case was an example of, um, a a,

0:04

a patient that had abnormal enhancement involving the optic nerve and

0:09

the optic nerve sheath on the left. And then when we look at the, uh,

0:14

T two weighted images, we can see these areas of,

0:18

let me window a little better here.

0:21

We can see these areas of, uh,

0:23

multiple white matter hyperintensities that are actually seen throughout the

0:26

brain parenchyma.

0:28

And this lesion right here kind of tips you off that we're probably dealing

0:31

with, um,

0:33

multiple sclerosis as opposed to metastases just because you have this sort of

0:37

rim of enhancement. And in a way it's this little,

0:40

sort of this thick and flare sequence too.

0:42

And then when you look at this lesion right here,

0:44

you can see it's sort of extending along the white matter tracks.

0:48

So when we look at the contrast enhanced study, uh,

0:53

we can see, uh, multiple lesions that are enhancing. Um,

0:58

and I think if someone did say lepto menal metastases,

1:01

I don't think that's necessarily, um, wrong. I think it's a good thought,

1:05

but sort of given the age of the patient and also given the orientations,

1:09

I think, um, uh, MS really is, is the best option.

1:13

So what I wanted to do, um, just really briefly is just give just a,

1:18

a couple of slides on optic neuritis.

1:21

So for the optic nerve itself, I know the classic thing,

1:26

and I kind of grew up with this as well too,

1:29

is that when we're looking at lesions that are involving the orbit,

1:32

we're always sort of trained to look at intracon versus extra conal. Um,

1:37

and to be honest with you,

1:38

the reason this kind of all developed is from the days of ct.

1:43

So unfortunately,

1:44

I grew up in the days of CT and really before we were doing m r,

1:47

the orbits and the most consistent anatomic structures that we could see in the

1:52

orbit were actually the extraocular muscle.

1:54

So we could see the superior rectus muscle.

1:56

You can see a little bit of the lator, paler muscle, medial rectus,

2:00

lateral rectus, inferior rectus. And these muscles actually,

2:05

um, form the cone of the orbit, if you will.

2:09

And that's how we sort of created this differential diagnosis of intracon versus

2:13

extra cline. I think that's actually, you know, taught, you know, for me,

2:17

what I've always liked to do is, um,

2:20

I think it's a little bit rudimentary just to look at the extraocular muscles

2:24

alone. So when you really do good imaging,

2:26

you should be able to see the optic nerve.

2:28

So this area surrounding is the dural sheath.

2:31

Then we have this area of increased T two signal, which is the C S F space.

2:36

And then right in the middle of that nerve, uh, that complex is the optic nerve.

2:40

So you have the optic nerve, the C s F, and then you have this dural sheet.

2:44

So for me,

2:45

I like to give my differential diagnosis based on the relationship of the optic

2:49

nerve as opposed to intracon versus extra conal because as you'll see

2:54

in this first week, um, there are a lot of masses that can

2:58

Occur in the orbit, but some of these, um,

3:01

are if can involve either within the cone or outside of the cone

3:06

and it can make things confusing. So I like to,

3:10

to give my differential diagnosis based on the optic nerve.

3:13

So this is what I was referring to today in the, in the old days, and this,

3:17

this was actually a very old study when I was actually a fellow down in,

3:21

in Gainesville, um, back in the last century. Um,

3:24

just nicely demonstrates that yeah, we can see the optic nerve,

3:28

but the most reliable features 30 years ago was actually the muscle cone.

3:31

So that's how it started. But moving forward again, we should be able to,

3:36

to base it on the optic nerve.

3:38

So this is an example of optic neuritis.

3:41

This is diffuse enhancement here involving the, the right optic nerve.

3:44

And then when we look at the coronal images,

3:46

we can see this very robust enhancement involving the nerve.

3:49

And you can see it on the opposite side. So when you do,

3:52

you do your intracranial versus extraoral differential diagnosis, yes,

3:56

optic neuritis is quote unquote in the differential for intracon lesions.

4:02

Now, if you, if, if you understand the anatomy of the optic nerve,

4:07

then you can actually begin to grade optic neuritis based on

4:12

what we see on good quality imaging.

4:15

So this is an example of unilateral optic neuritis and we can see the abnormal

4:19

enhancement of the nerve sheath.

4:21

And then when we look at the coronal T two weighted images with fat suppression,

4:25

we can see a little bit of increased signal here involving the nerve.

4:29

And if you look real closely,

4:31

you can actually see asymmetrical increased signal surrounding the C

4:36

S F.

4:36

And that really is a consistent finding when you have cases of optic neuritis.

4:41

In fact, um, at times when we look,

4:43

and I'll go over these in just a in a second,

4:45

when we start looking at the subacute and the chronic forms,

4:48

that asymmetrical signal in that C S F is actually a pretty reliable signal.

4:53

So in acute optic neuritis,

4:55

the main finding is really gonna be abnormal enhancement.

4:58

And then you may start to see some increased signal in the sheath.

5:02

Now what happens in subacute optic neuritis is that that signal goes away,

5:07

the enhancement goes away. But when you look at the T two weighted images,

5:11

look at this,

5:11

you can see the signal within the optic nerve is higher signal on the involved

5:15

side. And then you can see the high T two signal surrounding that optic nerve.

5:20

And to be honest with you, you know,

5:22

I would say the majority of cases of optic neuritis that I see are probably

5:27

somewhere in the peri subacute phase.

5:30

And occasionally by the time the patients develop this vision loss and they

5:34

think they have optic neuritis by the time they present to the ophthalmologist

5:38

or the optometrist and then they get their imaging study done,

5:41

sometimes that enhancement is completely gone away or it'll just see a little

5:44

bit. So to be honest with you,

5:47

I really take a really hard look at the coronal T two weighted images, um,

5:51

to see if I see those associated findings.

5:54

And then eventually in chronic optic neuritis,

5:57

What happens is that you can see that optic nerve right here and then eventually

6:00

it shrinks and it shrinks to almost like a pinpoint nerve. And then again,

6:05

look at the high signal surrounding the optic nerve on the right side compared

6:09

to the left side. So when you get really good in optic neuritis,

6:12

not only can you make the diagnosis,

6:14

but you can actually grade it based on the enhancement pattern and also the

6:18

caliber of the optic nerve and the surrounding T two signal. Now,

6:23

what has been described, um,

6:25

as we've learned more about optic neuritis and,

6:28

and actually about multiple sclerosis,

6:31

is that there sort different types and these are really based on specific as you

6:35

know, biomarkers, um, basically liquid biopsies if you will.

6:40

So the classic multiple sclerosis can give you this unilateral optic neuritis.

6:45

So this is just a classic case of left optic neuritis.

6:49

Now this was something that we used to call devex disease.

6:51

This is neuromyelitis optica and it's been identified to be associated with anti

6:56

aquaporin four. And so in dev X disease,

6:59

this is the classic thing about optic neuritis associated with abnormal signal

7:04

within the cervical cord. So you'd get these plaques in the cervical cord.

7:08

So in dev X disease, and I should say N M O is the,

7:13

is really the proper term. This, uh,

7:15

enhancement pattern has a tendency to be bilateral.

7:20

So you can see it bilateral here.

7:22

And this is more associated with aquaporin four.

7:25

And then this is something that's been described really has gotten a lot of

7:29

press over the last five to seven years,

7:31

is that now you can identify a form of a demyelinating process

7:36

that can result in,

7:38

in a type of optic neuritis that's called myelin oligodendrocyte,

7:42

oligodendrocyte glycoprotein or mog.

7:45

And M o G has a tendency to involve the anterior portion of the optic nerves and

7:49

it tends to be more severe. Now, uh, you know,

7:53

a few years ago when we started figuring out that there were different types of

7:57

optic neuritis, there was some thought that hey, maybe we could actually,

8:01

you know, identify the type of optic neuritis based on the enhancement pattern.

8:06

And it doesn't always work. But in general,

8:10

and this is really a rough rule,

8:12

if you see unilateral involvement of an optic nerve that's more consistent with

8:16

multiple sclerosis,

8:18

if you see bilateral involvement and especially involvement to the posterior

8:22

portion of the nerve as is seen here,

8:24

then that is a little bit more consistent with N M O.

8:28

And then if you see really robust enhancement involving the anterior half of the

8:32

optic nerves, especially with extending into the nerve globe junction,

8:35

that's more suggestive of M O G because these patients tend to have a, a,

8:40

a more robust form of optic neuritis, a more severe form. But again,

8:44

those are more rules of thumb than, than really hard rules.