0:01

A brief comment about anatomy.

0:03

So, clearly,

0:04

we're going to be focused on the white

0:06

matter as we talk about demyelinating

0:08

disorders and multiple sclerosis.

0:10

But as I said,

0:11

this has become a disease that we

0:15

understand has both gray matter impact,

0:17

as well as white matter impact.

0:19

And as you saw with the FLAIR post

0:22

contrast seven Tesla scanning,

0:24

even left domingal impact.

0:26

So we may see enhancing leptomeninges,

0:30

we may see enhancing gray matter

0:32

demyelinating plaques,

0:34

and we may see white matter plaques.

0:36

So it behooves us to understand a little

0:38

bit about the various white matter tracts

0:40

that are coursing through the brain.

0:42

And this, for example,

0:43

is just on the left hand side,

0:46

showing the corticospinal tracts and the

0:48

motor tracks going through the brain.

0:52

And also recall that we will have sensory

0:55

tracts that are also going to be

0:56

coursing through the brain.

0:57

And these demyelinating disorders can

1:01

affect anywhere along these tracks.

1:03

So it is a disorder that will affect both

1:06

the supratentorial white matter as well

1:09

as the infratentorial white matter going

1:12

through the brain stem and then

1:14

even into the spinal cord.

1:16

And we look for demyelination in the

1:18

entire central nervous system.

1:21

I want to focus just a moment on the

1:23

Trex in the spinal cord.

1:26

So,

1:27

from our sagittal scan,

1:29

we are usually looking at the spinal cord

1:33

with our T two weighted and STIR pulse

1:36

sequences in a sagittal plane.

1:38

And then, as I mentioned previously,

1:40

in the axial plane,

1:41

we're using fastbane echo T2-weighted

1:43

scan as well as gradient

1:45

echo T2-weighted scan.

1:46

Where should we be looking

1:48

for demyelination? Well,

1:50

as you recall from your days

1:52

looking at anatomy books,

1:55

the spinal cord has central gray matter

1:59

but peripheral white matter tracks.

2:03

So, in general,

2:04

we say that you should be looking along

2:06

the periphery of the spinal cord

2:08

for demyelinating plaques.

2:10

It happens that the posterior

2:12

columns represented here

2:16

in the vesiculus cuniatis and gracilis,

2:20

these posterior columns have a particular

2:23

predilection for demyelination.

2:26

But you will see demyelination

2:28

all over the spinal cord,

2:31

generally sparing the central

2:33

gray matter area.

2:35

One anatomic structure that we should be

2:38

very cognizant about is the

2:40

virchow-robin space.

2:42

The Virchow-Robin space is the CSF space

2:46

that occurs around blood vessels,

2:48

usually small vessels,

2:49

and often the arteries or the veins.

2:54

And this CSF is going to look bright

2:59

on our T2-weighted scan.

3:01

This is the value of FLAIR scanning

3:04

because CSF on FLAIR is dark

3:07

in signal intensity,

3:09

whereas CSF on T2-weighted scan

3:12

is bright in signal intensity.

3:14

Demyelination on FLAIR is bright in signal

3:19

intensity. On T2-weighted scan,

3:21

demyelination is bright.

3:23

So on a T2-weighted scan,

3:25

sometimes you can't tell the difference

3:27

between a perivascular space and

3:30

demyelination, whereas on FLAIR scan,

3:33

because the perivascular space is dark

3:37

but the demyelination is bright,

3:39

it's very helpful.

3:40

So going back to this initial scan that

3:43

I set of scans that I showed at

3:46

the beginning of this session,

3:48

if we look at our T2-weighted scans,

3:51

at the bottom,

3:53

we see all of these bright areas

3:57

throughout the frontal lobes

4:01

that are brightened signal intensity

4:04

on our fastbanecho T2-aid scan.

4:09

However, when we turn to the FLAIR scan,

4:13

many of these bright areas are actually

4:17

dark in signal intensity

4:22

on the FLAIR scan.

4:24

So this little series of dark signal

4:27

intensity in the subinsular region on the

4:30

FLAIR corresponding to the bright

4:33

area on T2-weighted scan,

4:35

these are the perivascular spaces.

4:38

They are dark on FLAIR but bright

4:41

on T2-weighted scan.

4:42

So we cannot rely on bright signal

4:46

intensity on fast beneco T2-aid scan as

4:49

a marker for demyelination. In every case,

4:52

we have to then correlate

4:54

it with the FLAIR scan.

4:55

The areas of demyelination on this FLAIR

4:58

image are actually those periventricular

5:01

zones over here,

5:04

which are bright in signal intensity

5:07

on FLAIR imaging.

5:09

So it's a combination of T2-aid scans

5:13

and FLAIR scans that allow us to

5:17

distinguish between the Virchow-Roban

5:21

perivascular spaces

5:24

versus

5:26

MS and demyelination.

5:31

I want to make one other point,

5:33

and that is that demyelination on FLAIR is

5:38

not as well demonstrated in the brain stem

5:41

as demyelination on T2-weighted scan.

5:44

So the one area where I use T2

5:46

aid imaging more than FLAIR

5:50

is in the brain stem

5:54

and end,

5:55

they're about equal in the cerebellum.

5:58

So you look at the T2-weight

6:01

scan for infratentorial

6:07

and rely on that most for infratentorial

6:10

demyelination.