0:00

Another of the causes of optic neuritis,

0:04

besides multiple sclerosis and viral infectious inflammatory

0:08

etiologies, is the neuromyelitis optica syndrome.

0:14

In this case, we have a patient who had left-sided visual loss.

0:19

As we scroll the images,

0:21

we again see abnormal signal intensity

0:24

in the left optic nerve.

0:28

This is seen well on the T2-weighted scan with bright

0:31

signal intensity in the optic nerve, and we notice that

0:34

the optic nerve sheath complex is not enlarged.

0:37

It is, however, showing contrast enhancement.

0:43

As we look at the remainder of the study of the brain,

0:47

I want to highlight one aspect on the post-gadolinium

0:51

axial scan of the orbit.

0:55

So, I'm going to bring down

0:58

the image of the magnified orbit,

1:04

post-gadolinium fat-suppressed image.

1:07

Something is different about this case than the previous

1:11

cases of optic neuritis that I showed, and that is that

1:16

this is a relatively large lesion

1:20

shown here on the post-gadolinium

1:25

axial scan, extending over a larger dimension of the

1:29

optic nerve compared with the previous cases.

1:34

Let's just scroll and verify that.

1:38

You see that it extends almost to the optic canal.

1:43

A long segment optic nerve lesion is more typical

1:49

of the neuromyelitis optica spectrum disorder.

1:54

Just as in the spine,

1:57

longitudinally extensive transverse myelitis,

2:01

where the lesions in the spine are

2:04

extensive in superior-inferior dimension.

2:07

It's more common in the neuromyelitis optica spectrum

2:10

disorder than in multiple sclerosis.

2:13

We say, in multiple sclerosis,

2:15

the lesions in the spine are usually one to two

2:17

vertebral segments, whereas for neuromyelias optica

2:21

spectrum disorder, or what we're going to call NMO,

2:24

it is usually over three segments long.

2:27

One of the other distinguishing features about

2:30

neuromyelitis optica spectrum disorder is the

2:34

appearance of the lesions in the brain.

2:37

Most of the lesions in the brain with

2:39

NMO occur in the posterior fossa.

2:44

As I said previously,

2:46

it's better to look at the posterior fossa structures

2:49

with the T2-weighted scan, rather than with a FLAIR scan

2:53

because demyelination is better seen on the T2-weighted scan.

2:58

Unfortunately, in the posterior fossa,

3:00

you have the potential for phase ghosting artifacts.

3:03

In this case,

3:04

we see that the patient has a white matter lesion,

3:08

which is seen in the edge of the medulla,

3:10

near the inferior fourth ventricle.

3:13

This white matter lesion is in a typical location for

3:16

neuromyelitis optica, which is the area postrema.

3:20

This is a portion of the brainstem that seems to have

3:25

correlation with the sense of nausea and vomiting.

3:29

The other area where NMO affects,

3:33

but multiple sclerosis generally does not affect,

3:36

is along the region of the hypothalamus.

3:39

So as we scroll more superiorly,

3:42

where we would be looking for, is lesions in this area.

3:50

And you see that there are a few little dots of abnormal

3:53

signal intensity in the region of the hypothalamus,

3:57

which is typical of NMO.

4:00

This is again a subtle finding,

4:02

but one that you want to look for,

4:03

particularly if one uses high-resolution imaging

4:07

of the brainstem and the hypothalamus

4:11

on T2-weighted imaging. Given these findings,

4:13

we would next want to scan the spine.

4:16

Now, initially,

4:18

NMO was thought to be a monophasic disorder, in which the

4:22

optic neuritis occurred at the same time as the spinal lesions.

4:28

That has since been discredited.

4:30

And therefore, we do recognize NMO as

4:33

a polyphasic, multiphasic disorder.

4:36

In which case, the optic neuritis and the transverse

4:40

myelitis need not be concurrent.