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This is an MRI of the brain

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in a three-year-old child

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that was referred in for a reported

0:07

Dandy Walker spectrum malformation.

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Anytime someone comes in with a diagnosis

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like that, I always start from scratch

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in my evaluation.

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I don't take for granted that the entity was

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characterized accurately.

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For two reasons.

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One is,

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there's different terminology

0:27

used in different places.

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Number two,

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a lot of the characterization performed when

0:32

someone is very young can be difficult to fully

0:36

understand the entire malformation.

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So, it may be that,

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at a young age,

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we thought it was a certain degree of severity

0:45

or a certain type of malformation.

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But as the brain matured, grew, myelinated,

0:51

that we can better understand what's going on.

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So, I start from the beginning,

0:57

and I can see there is cystic prominence

1:01

of the posterior cranial fossa.

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There is continuity between that cystic

1:07

prominence with the fourth ventricle.

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If I go to this sagittal image,

1:13

we see there's a hypoplastic

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cerebellar vermis that is uplifted,

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and the fourth ventricle is in free continuity

1:21

with this cystically enlarged

1:23

posterior cranial fossa.

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I also can tell that the nuchal ligament

1:29

inserts right here, and there's a little bump,

1:32

which is likely the external

1:34

occipital protuberance.

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And the torcula is actually right here.

1:39

And that little bump right there is the

1:41

internal occipital protuberance.

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So the torcula isn't markably elevated relative

1:47

to the position of the nuchal ligament.

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That is a sign of an enlarged posterior cranial fossa.

1:53

And that was something that,

1:56

on a lateral skull radiograph,

1:58

could be used to raise question

2:00

about a possible Dandy Walker malformation

2:03

in the era of plane films.

2:05

That's not the only finding that we see.

2:07

Yes, this is a classic Dandy Walker spectrum malformation

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with a very hypoplastic uplifted

2:15

cerebellar vermis and markably dilated

2:17

posterior cranial fossa.

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But if you look closely,

2:21

there is absence or agenesis

2:23

of the corpus callosum.

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With that,

2:26

we see absence of the cingulate gyrus.

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We see parasagittal gyri that extend to the

2:33

third ventricle and radiate outward.

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We can see here that there's a parallel

2:40

appearance of the body of the lateral ventricles.

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And on this coronal image,

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along the medial aspect of the parallel body of

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the lateral ventricles is this white matter

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bundle known as the probes bundles,

2:55

which are anterior posteriorly

2:57

directed fiber bundles.

2:59

That are fibers that were intended to come

3:05

commissural fibers,

3:06

traversing the midline

3:07

through the corpus callosum.

3:08

There's a vertically oriented third ventricle

3:11

with direct continuity with the

3:14

interhemispheric fissure.

3:15

There is a relatively low position of the distal

3:21

branches of the anterior cerebral artery.

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These normally would be called

3:25

the pericallosal artery,

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but I'm not sure if we can call it the

3:28

pericallosal artery if there's no corpus

3:31

callosum for it to wrap around.

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But there's a caudal position of the distal

3:35

branches of the anterior cerebral artery.

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So this patient has a classic

3:39

Dandy Walker malformation,

3:41

but also agenesis of the corpus callosum.

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The constellation of findings definitely

3:48

warrants further evaluation with genetic testing.

3:52

In recent years,

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we've learned that one class of abnormalities

3:57

that can result in this combination

4:00

includes abnormalities of the tubulin gene,

4:03

or tubulinopathies.

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So, this patient may benefit from a genetics

4:08

consultation and evaluation for abnormalities

4:11

such as a tubulinopathy.