0:00

Alright, another pediatric case.

0:03

Uh, this one with complaints of headache

0:07

and in the child we see a mass

0:12

that appears to be growing from the posterior fossa

0:15

inferiorly into the upper cervical spine

0:19

on the Sagal T.

0:20

One way it scan on the flare scan it's a lesion which is

0:25

reasonably bright

0:26

but does course into the upper cervical spine

0:29

as you can see there.

0:31

And this lesion is causing some ventricular enlargement.

0:37

Don't see that dramatic transanal CSF flow that we saw

0:41

with the previous case,

0:42

but this is big ventricles for a child,

0:45

particularly those temporal horns.

0:47

And we see why because

0:48

of the mass effect on the fourth ventricle as well

0:51

as the outflow of the fourth ventricle.

0:54

Now this lesion as you can see, could

0:57

represent a midline lesion and

0:59

therefore be in that category

1:02

of the H three K 27 M glioma.

1:06

What makes this not that high grade tumor?

1:11

Well the features that are important

1:13

to recognize are number one,

1:14

that the enhancement is very well-defined.

1:18

And this is a case

1:20

where the A DC maps are very helpful to us.

1:25

The A DC maps of the mass

1:28

show a mean value of 1 4, 6 5,

1:32

and one voxel 1, 4 6, 1 or another voxel.

1:35

Let's go to a different section

1:38

and put in another rectangle here

1:41

and take the mean value 1 3 7 8.

1:46

So those values are not representative of a

1:51

high grade astrocytoma

1:54

or those high grade midline gliomas.

2:00

In fact, there's an outstanding paper that I'd love

2:03

to reference by Zoran Rumble.

2:05

Unfortunately, Zoran um, passed away a couple years ago.

2:08

Uh, he's a pediatric neuro radiologist

2:10

who was a superb individual and a fantastic physician.

2:14

And he looked at the A DC values

2:18

of posterior fossa tumors in children

2:21

and he looked at the three main categories,

2:24

those being the medulloblastomas, the appendamoma,

2:28

and the juvenile pilocytic astrocytomas

2:31

or grade one astrocytomas.

2:34

And what he found was you can have a very good separation

2:38

of these histologic variants

2:40

based on looking at the A DC values.

2:43

Medulloblastomas we all know are high grade grade four

2:46

tumors and they're usually hypercellular.

2:49

Those tumors had a DC values

2:53

that were less than 600 when he looked at

2:57

the patients who had

2:59

Appendamoma.

3:00

There was a wider spread of values for appendamoma, but by

3:04

and large most of them fell between 800

3:08

and 1200 on the a DC values.

3:13

He then looked at the patients

3:14

who had pilocytic astrocytomas grade one astrocytomas,

3:17

and nearly all of them had a DC values

3:21

that were greater than 1200.

3:24

So it was actually a beautiful study

3:27

and it was very helpful.

3:29

So if you see something that has an A DC value less than 800

3:33

and has imaging features that are consistent with it,

3:36

that's pretty good for medulloblastoma.

3:38

Between 800 and 1200, obviously we have our PFA

3:42

and PFB appendamoma that are gonna look different,

3:45

asymmetrical, higher grade, et cetera.

3:48

But those a DC values generally fall between 800 and 1200.

3:52

As I look at this case with a mean A DC value

3:56

of 1,378

3:59

that's in the low grade astrocytoma category.

4:03

And this was indeed a graph

4:07

V 600 E low grade astrocytoma

4:12

of the posterior fossa growing into

4:15

the upper cervical spine.

4:17

So just the exquisite case showing that great value

4:23

of measuring the A DC in posterior fossa tumors.

4:26

I hope that was helpful to you. A great tip.