0:00

This is an MRI of a child

0:02

who's five and a half years old

0:04

with developmental delay.

0:05

And if we look at the mid-sagittal

0:07

T1-weighted imaging,

0:08

we're not seeing what looks like

0:10

a normal corpus callosum

0:11

similar to the patients with the agenesis of

0:14

the corpus callosum, which we saw before.

0:16

We have a parallel appearance of the

0:18

body of the lateral ventricles,

0:20

and we have mild enlargement of the atria and

0:22

occipital horns of both lateral ventricles,

0:24

left greater than right,

0:25

sort of a milder version of colpocephaly than

0:28

in some of the other cases that we've seen.

0:30

Now,

0:31

this is not a true agenesis of the corpus callosum,

0:34

because if we look here,

0:35

we actually see some midline commissural fibers

0:39

in a portion of the corpus callosum.

0:41

If we go back to the mid-sagittal image,

0:43

we see a very, very small area.

0:46

So, this is not complete agenesis of the corpus

0:49

callosum, which means complete absence.

0:51

But this is definitely a very severe dysgenesis

0:53

or abnormal development of the corpus callosum.

0:56

In terms of other commissural fibers,

0:58

we see a small anterior commissure right here.

1:02

Otherwise,

1:03

all the other features of agenesis of

1:05

the corpus callosum seem present.

1:07

We're seeing a low position of the distal

1:10

branches of the anterior cerebral artery,

1:12

which would have been the pericallosal artery.

1:14

We're seeing absence of a cingulate gyrus.

1:17

We're seeing these radiating gyri.

1:19

So normally, the parasagittal gyri of a cerebral

1:22

hemisphere stops at the level of the cingulate gyrus,

1:27

which goes anterior posteriorly,

1:29

whereas here, we're not seeing it.

1:30

And so, we have these gyri that

1:32

radiate all the way out.

1:34

The corpus callosum would normally be here

1:37

with the cingulate gyrus above it.

1:39

Given that that's absent,

1:41

this area here becomes relevant because we have

1:44

these gyri that radiate all the way

1:47

out from the third ventricle,

1:48

whereas if there was a cingulate gyrus present,

1:51

that would not be present.

1:52

On the coronal image,

1:54

we also see a vertically oriented third ventricle,

1:56

and a lot of things that look,

1:58

the configuration looks somewhat similar to

2:00

the agenesis of the corpus callosum cases,

2:03

but we actually do see a portion of the

2:06

corpus callosum in the midline.

2:08

This dark area here on this STIR image

2:11

are myelinated fibers

2:12

in the remaining portion of the corpus callosum.

2:15

So, this is a patient with severe dysgenesis of

2:19

the corpus callosum, but not complete agenesis.