0:01

This was a scan of a child that was being

0:04

evaluated for recurrence of medulloblastoma.

0:10

On the T1-weighted scan,

0:12

before contrast,

0:13

we note that the signal intensity of the

0:16

vertebral body is just a little bit more

0:18

bright on the T1-weighted scan

0:20

than one would expect.

0:21

This is yellow fatty marrow replacement for

0:25

from radiation therapy.

0:26

I noticed that also that the skull base,

0:28

the patient has had surgery for the

0:31

medulloblastoma. But even on the T1-weighted

0:34

scan, if we just magnify a little bit,

0:37

we see in the thoracic region that there are

0:40

these areas of nodularity on the surface of

0:44

the spinal cord with some widening of the

0:46

subarachnoid space. As I mentioned,

0:48

for subarachnoid seeding, really,

0:50

we need post-gadolinium-enhanced scans,

0:52

the T1-weighted and T2-weighted scans,

0:55

unless it's pretty gross

0:56

disease like this, are often negative.

0:59

So when go to the post-gadolinium-enhanced images,

1:03

you can see very thick contrast enhancement on

1:08

the posterior portion surface of the spinal

1:11

cord, indicative of subarachnoid seeding.

1:15

There are some areas also on the anterior

1:17

aspect at the C6 level.

1:20

So I went back to look at the prior studies on

1:23

this patient to see where the subarachnoid

1:25

seeding was in the past that they were looking for.

1:30

So if we go back to the patient's earliest

1:33

most study and just pull up some

1:37

representative images, pre and post-contrast.

1:40

This is the flare scan.

1:42

We see this large infiltrative

1:44

mass in the posterior fossa,

1:47

predominantly in the midline,

1:48

but extending to the right side.

1:50

And it just looks kind of aggressive the way

1:53

it has enhancing areas, as well as non

1:57

enhancing areas, but just sort of

2:00

infiltrating the fourth ventricle

2:01

and leading to hydrocephalus.

2:03

So medulloblastomas are grade four,

2:08

the most malignant of the brain tumors.

2:12

Usually on the ADC maps,

2:14

they're going to be dark in signal intensity.

2:16

So this is diffusion-weighted scan.

2:18

I'll bring up the diffusion-weighted image.

2:20

So bright on the diffusion-weighted image,

2:22

but dark signal intensity on the ADC map,

2:27

reflecting low ADC,

2:29

which is usually a marker of hypercellularity.

2:32

And this is very typical of a medulloblastoma

2:35

in the posterior fossa. On this scan,

2:38

the patient did have surveillance for

2:42

subarachnoid seeding, and on the post

2:46

gadolinium-enhanced scans, while you see some

2:49

of the enhancement of the

2:50

posterior fossa mass,

2:52

the scans through the spinal cord looked

2:56

pretty normal. However, the CSF was positive.

3:00

So this is an example of a patient

3:01

who had medullobastoma,

3:03

who had a relatively negative cord

3:05

evaluation, pre and post-contrast,

3:07

but had positive CSF in there.

3:09

And then in follow up, and again,

3:11

the follow up that I was looking at was four

3:13

years after the initial resection of the tumor,

3:16

had all of this bad subarachnoid seeding.

3:20

Just to make the point on the examination of

3:24

the brain, the only area of concern on the study.

3:29

It looks like they got the primary tumor pretty well,

3:32

except there was this one small area of

3:34

enhancement which could represent subarachnoid

3:37

seeding of the ependymal surface of the

3:39

fourth ventricle, and then an additional seed

3:42

at the interpeduncular cistern of the midbrain.

3:45

So in this case,

3:47

the primary tumor was taken care of,

3:50

but unfortunately,

3:51

the subarachnoid bread of the tumor was what

3:54

was the main issue in four year follow up.