0:00

We've got a 54-year-old woman,

0:02

presents with bilateral foot drop

0:04

and dragging both feet for six weeks.

0:08

That's not a very specific history.

0:10

But yet, it does tell an important story.

0:13

Certainly, something happening with the cord or the spinal

0:17

canal affecting the cord.

0:19

And I'm here with my colleague,

0:21

fellow neuroradiologist and expert, Ben Lazar.

0:25

And we're looking at this gal's cord on a sagittal T2.

0:30

On your far left, no fat suppression added.

0:33

In the middle, we have a contrast-enhanced T1,

0:37

and on the right, we have a modestly fat

0:41

suppressed contrast-enhanced T1.

0:44

That's probably the most impressive of the images,

0:47

but we both know the diagnosis.

0:50

But I'd ask you to zero in on what bothers

0:54

you about the Sagittal T2.

0:56

So, two things on the sagittal T2 bother me.

0:59

One,

1:00

there's this vague increased signal

1:02

within the spinal cord.

1:03

Essentially, lower thoracic spine that is ill-defined.

1:09

It has no mass effect.

1:10

It's not expanding the cord.

1:12

The cord is still normal in contour

1:15

and shape. Most people would blow by that,

1:19

don't you think? I think so too.

1:21

It's very subtle when you correlate it with the other

1:23

images, sure, it makes it a little easier.

1:26

So the Sagittal T1, and this is admittedly difficult,

1:30

but when you really window it and you administer contrast,

1:34

there is a faint blush of enhancement,

1:37

especially right there.

1:39

Again, that is another finding that you

1:42

could completely blow over.

1:44

And it's totally explainable why 34567 MRIs are done on

1:49

this patient and nobody comes up with an explanation.

1:51

Making matters worse is look how big the field of view is.

1:55

So you might be looking for tiny little peel vessels,

1:59

as in a Dural AVF.

2:01

Now, you're probably not going to miss a type two intramedullary

2:06

dural AVM because those are easier to see with flow voids.

2:10

But dural AVFs, they're tiny.

2:12

They're less than a millimeter in size.

2:14

So when you have low-res imaging or large fields of

2:17

view like you usually have with a thoracic spine,

2:20

you're going to miss the abnormal vessels that are seen in

2:24

the intradural space. Now, we shunt over here to our,

2:29

pardon the pun shunt.

2:30

We shunt over here to our axial contrast

2:33

enhanced fat suppression image,

2:35

and we've got this funny little owl's eye sign.

2:37

In fact, it looks like ET.

2:40

The extraterrestrial there are the two eyes of ET right

2:43

there, and the shape of the head is pretty good.

2:45

So now that we see that the lateral column has abnormal

2:50

enhancement, we're confident that we have an abnormality.

2:53

So beside provides a vascular abnormality,

2:57

like a type one dural AVF, which is the most common.

2:59

70% of all of them.

3:01

What is in our differential diagnosis?

3:04

Let's just tick down the differential.

3:06

So pick one. One demyelination.

3:09

Demyelination, okay, let's talk about that.

3:12

What goes against it?

3:14

What goes against it is typically demyelination is going

3:17

to be peripheral wedge-shaped along the cord,

3:20

typically dorsal spinal cord. In this case,

3:22

it's more central, it's more lateral enhancement.

3:26

But on the T2,

3:27

you can see that the abnormal signal is pretty

3:29

much within the center of the cord.

3:31

And skip areas, too. And skip areas.

3:33

What about a viral myelitis?

3:35

That comes up a fair amount.

3:38

Somebody sees a high signal in the cord.

3:41

I've been a trained radiologist for longer

3:42

than I care to acknowledge.

3:44

Usually, the first thing that comes out of their mouth is,

3:47

well,

3:47

I can't rule out, but then they say can't rule out

3:50

myelitis, and it's just something familiar to them.

3:55

And then I ask them what kind of myelitis?

3:58

And they usually say, well, viral or infectious.

4:01

So

4:03

would a viral myelitis or any kind of

4:06

infectious myelitis even fit here?

4:09

Probably not typically infectious myelitis.

4:13

A, the enhancement pattern is going to be different,

4:16

and B,

4:17

you're going to see more expansion of the cord and

4:20

the length of the lesion is going to be yeah,

4:22

it's usually not so far up.

4:24

The cord is often swollen.

4:26

Admittedly, the enhancement pattern is pretty variable.

4:30

But another key thing is somebody with a myelitis that's

4:33

infectious. It comes on like, really acutely.

4:36

And this is a condition that gradually, gradually,

4:38

slowly ascends and produces lower motor neuron signs.

4:43

So clinically, they don't look alike at all.

4:46

And that is also true of the toxic myelidities, too.

4:49

You can get it from toluene and heroin and valproic

4:53

acid and a bunch of other toxins.

4:55

Lead, even porphyria, is in a way,

4:58

a toxin that results in a myelitis.

5:01

So it doesn't really fit for a myelitis.

5:04

Now, you do get cord signal alteration,

5:07

gliosis and myelomalacia from DJD, but that one's easy,

5:11

right? We don't have DJD, we don't have cord compression,

5:14

so we don't have signs of arterial insult.

5:18

Then you get into something like diabetes mellitus,

5:21

severe small vessel disease.

5:23

That can be a real difficult one to exclude.

5:26

More often than not, though,

5:27

they have really severe peripheral neurologic dysfunction.

5:32

And I haven't seen that many cases over my lifetime

5:35

of diabetes predominantly affecting the cord,

5:37

and it's not a long level abnormality.

5:41

What about Guillain-Barré syndrome?

5:43

So Guillain-Barré syndrome, typically you would see,

5:46

especially on the post-contrast images,

5:48

really bright cauda equina nerve roots,

5:50

and it typically ascends from the cauda equina to the head.

5:54

You would see the cauda equina nerves being enhancing,

5:58

and then the spinal cord from the conus extends.

5:59

Ending up, and in this case, we don't really have that.

6:02

It looks like it coats the surface of the cord.

6:05

It's kind of weird-looking.

6:06

And Guillain-Barré is mostly motor.

6:09

It gets into the respiratory system, and you

6:11

got to put the patient on a ventilator.

6:13

But there is a sensory form of Guillain-Barré

6:15

seen about 5% of the time.

6:18

These patients are also motor patients,

6:22

patients with Dural AVFs,

6:23

although eventually they do get a sensory level,

6:27

but the appearance is not consistent.

6:30

Even though you do have this filmy pattern of enhancement,

6:33

it's a little more intense with Guillain-Barré and

6:36

as you said, nerve roots from the bottom up.

6:38

And this one is right about at T nine,

6:41

which is probably the most common site where you're

6:43

going to see the epicenter of a Dural AVF.

6:47

Then we've also got these lateral areas of enhancement

6:50

on the axial fat suppressed image,

6:53

which is not typical at all for Guillain-Barré syndrome.

6:57

One of your colleagues mentioned subacute combined

6:59

degeneration with deficiency of vitamin B twelve

7:04

pathway. That can give you an Alzheimer's,

7:07

but it is a posterior column disease,

7:10

so it's usually more in the back.

7:11

And they don't have this uber long pattern of involvement.

7:16

The enhancement is scant to none,

7:18

and it's an easy diagnosis to exclude by laboratory

7:22

methods. I think we'll stop right there,

7:24

unless you have any other thoughts.

7:25

No? Great. Thank you.