0:00

This was a two-year-old who presented with failure

0:04

to thrive and not meeting milestones.

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On the T1-weighted scan,

0:08

we look at the brain and we assess it as showing

0:13

a normal size, so no evidence of macrocephaly.

0:18

On the FLAIR scan,

0:20

we see a white matter disease,

0:22

which is predominantly central in its

0:25

location and is symmetrical.

0:27

We also note that the patient has an arachnoid cyst

0:31

which is causing remodeling of the

0:33

greater wing of the sphenoid.

0:35

But let's dispense with that because that's irrelevant

0:37

to the case of a dysmyelinating disorder.

0:41

This dysmyelinating disorder affects

0:42

both the genu and the splenium of the corpus callosum.

0:45

But what one can see is that it spares

0:48

the subcortical U fibers.

0:50

So we see the involvement centrally,

0:53

but you're not seeing involvement going

0:55

out to the subcortical U fibers,

0:58

which would be typical of other dysmyelinating

1:01

disorders other than this case,

1:03

which is metachromatic leukodystrophy.

1:06

Since metachromatic leukodystrophy is the

1:09

most common of the dysmyelinating disorders,

1:11

we might want to look for the so-called tigroid

1:14

stripes that are characteristic

1:16

of this dysmyelinating disorder.

1:19

For the tigroid stripes, we look at the

1:24

periphery of the ventricles,

1:27

and we see the little dots of the

1:31

somewhat spared white matter.

1:33

Let me demonstrate this.

1:35

So in this case,

1:36

you see these little dots where

1:38

there is not homogeneous dysmyelination,

1:41

but there appear to be little areas of darker signal

1:44

amidst the FLAIR abnormality of the dysmyelination.

1:49

In point of fact,

1:50

if we look at this particular image,

1:53

we can identify the characteristic feature

1:57

of those tigroid stripes.

1:58

So, here we see dark signal intensity

2:02

going out to the periphery.

2:03

Here's another area of these stripes of white matter

2:09

that is not involved with the dysmyelinating disorder.

2:13

At the same time that you can see some of the dots of

2:17

white matter fibers that have been cut in cross

2:21

section as they are coursing superiorly in the brain.

2:25

So, this characteristic of sparing of these

2:28

subcortical U fibers and the tigroid stripes

2:31

leads us to the diagnosis of metachromatic leukodystrophy.

2:36

We can also verify this when one looks

2:39

at the MR spectroscopy

2:41

that was performed at the same time

2:45

on this patient.

2:47

And what one sees on the MR Spectroscopy

2:50

is depression of the NAA,

2:54

not elevation of the NAA.

2:57

So, in the differential diagnosis of metachromatic

3:00

leukodystrophy is Canavan's disease,

3:02

where we would expect to see the big NAA spike

3:05

and the lower choline and creatinine spikes.

3:09

In this case, we see that the NAA is,

3:12

if anything, somewhat lower,

3:13

which confirms the diagnosis of metachromatic

3:16

leukodystrophy by virtue of absence of NAA elevation.

3:21

We also do not see the macrocephaly,

3:24

which is typically of

3:25

Canavan's disease and Alexander's disease.