0:01

So you're down in the emergency department, and once

0:03

again, you're called by the clinicians and by the

0:07

MR. techs that there's a patient who is, uh, having

0:11

difficulty in the scanner, moving all over the place.

0:15

The history was changed in mental status, and the

0:17

patient's a little bit combative and not themselves.

0:20

You look into the medical

0:21

history; the patient has leukemia.

0:24

So all they got was diffusion-weighted

0:26

scans and some motion-blurred flare scans.

0:29

You look at the motion-blur flare scans,

0:31

and you say, well, this is non-diagnostic.

0:34

Can't really do very much with that.

0:36

Oh, well, on the diffusion-weighted scan, however,

0:39

the patient was able to hold still. What?

0:41

Why is that?

0:42

Diffusion-weighted scans in general,

0:44

take about 50 seconds to perform.

0:47

The flare scans about four minutes, 10

0:49

seconds, at least at Hopkins, to perform.

0:52

So the patient was able to hold

0:53

still on the diffusion-weighted scan.

0:55

And lo and behold, you notice that there is bright

0:58

signal intensity bilaterally in the white matter

1:02

of the centrum semiovale and corona radiata.

1:06

Of both hemispheres.

1:08

Once you see this bright signal intensity, you

1:10

go back to the flare, and you say, well, I'm not

1:12

really seeing anything bright on the flare scans.

1:16

Is that just because the patient's moving?

1:19

Not really sure.

1:20

What we do have, however, is the ADC maps.

1:23

And on the ADC maps, you note that that bright

1:26

signal intensity corresponds to dark signal on

1:29

the ADC map, suggesting restricted diffusion.

1:33

So this is a leukoencephalopathy with restricted

1:36

diffusion that is only seen on the diffusion

1:40

weighted scan and is not seen on the bad quality

1:44

flare scan.

1:45

This is a pattern that you

1:46

should recognize as being toxic.

1:49

Glucocerebrosidase encephalopathy, again,

1:51

usually secondary to medications.

1:54

In a patient who has leukemia or lymphoma, the

1:57

drugs that can do this include methotrexate,

2:01

and that may be intravenous methotrexate,

2:03

or it may be intrathecal methotrexate.

2:06

In this case, the patient was receiving intravenous

2:09

methotrexate and has a leukoencephalopathy.

2:12

Secondary to the methotrexate, accounting for

2:16

the change in mental status, and this is one

2:19

of the few entities that's going to be bright

2:22

and abnormal on the DWI, but negative on the

2:27

flare scan, even if it was a good quality scan.

Case: Toxic Leukoencephalopathy on MRI

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