0:00

This patient presented with a classic history of change

0:04

in mental status.

0:05

The bane of the radiologist's existence,

0:08

at least the neuroradiologist.

0:10

So, let's scroll through this case.

0:12

So, this is a patient who has a

0:15

very large bilateral lesion,

0:18

and it has heterogeneous signal

0:21

intensity on FLAIR image,

0:23

including mass effect on the frontal horn

0:26

of the right lateral ventricle.

0:30

As we look at it on diffusion-weighted scan,

0:33

we see the vast majority of this is...

0:37

on the ADC map, is showing T2 shine through,

0:40

although there is a periphery of dark signal intensity

0:43

which might suggest cytotoxic edema.

0:47

At this point,

0:47

we really don't know what this might be.

0:50

The leading thought would be a glioblastoma

0:55

that may be crossing the corpus callosum,

0:57

which appears to be expanded.

0:59

Let's look at the postgadolinium enhanced images.

1:03

This is a 3D gradient echo T1-weighted scan.

1:08

And what is curious about this lesion is that it has

1:11

that peripheral pattern of contrast

1:14

enhancement of an incomplete rim.

1:18

Not only that,

1:19

but what looked like two separate lesions can be seen to

1:23

be joining here across the corpus callosum as a single,

1:28

intact,

1:30

large right greater than left lesion.

1:33

On our coronal image,

1:34

although there is motion artifact,

1:36

that persistent peripheral incomplete rim of enhancement

1:43

is identified,

1:45

leading one to be less sure that this represents a

1:52

neoplasm and more likely represents

1:55

tumefactive demyelinating disorder.

1:59

The next step would be to pull down

2:02

our perfusion-weighted scans.

2:05

This is cerebral blood volume corrected.

2:09

And on this grayscale,

2:11

what we see is that the ventricles

2:16

are dark in signal intensity,

2:18

showing low cerebral blood volume.

2:22

The gray matter is red in color,

2:26

which is our marker for something that has high cerebral

2:30

blood volume.

2:31

As we get to our lesion,

2:33

we see that it is predominantly purple, not red,

2:36

and therefore has low cerebral blood volume.

2:41

And that would be distinctly unusual for a

2:44

high-grade astrocytoma.

2:47

For that reason,

2:48

we would suggest instead that this represents a

2:52

tumefactive demyelinating lesion,

2:54

which was confirmed at surgery.