0:01

This is an MRI of the brain

0:02

in a six-year-old child with seizures,

0:05

that at an outside institution

0:10

was referred to as a Dandy-Walker variant.

0:14

Now, if we look,

0:17

we see the normal development

0:19

of the cerebellar vermis,

0:21

and that normal development of

0:23

the cerebellar vermis tells us

0:26

that this is not a Dandy-Walker

0:27

spectrum malformation.

0:29

There is no hypoplasia or

0:32

intrinsic developmental abnormality

0:34

within the cerebellar vermis.

0:36

Now, there is prominence of CSF

0:40

posterior and inferior to

0:42

the cerebellar vermis.

0:44

And if we look on this axial image,

0:46

this CSF prominence is on both

0:49

sides of the falx cerebelli,

0:51

and it goes behind both

0:53

cerebellar hemispheres.

0:55

It's hyperintense on T2-weighted imaging,

0:58

suppresses on FLAIR imaging,

1:01

and demonstrates facilitated diffusion.

1:04

So, this is an arachnoid cyst.

1:07

There is no significant mass

1:10

effect upon the cerebellum.

1:12

I think this more likely is,

1:15

given the absence of contra abnormality,

1:18

just chronic remodeling and

1:21

chronic slight expansion of the

1:23

posterior cranial fossa.

1:25

We also see chronic elevation of

1:29

the torcula and the superior

1:32

angulation of the posterior

1:33

aspect of the straight sinus

1:36

related to this.

1:38

So, this is a retrovermian arachnoid cyst

1:42

that's also infravermian.

1:44

But there is no Dandy-Walker spectrum malformation.

1:47

So, that's very important

1:49

that there is not a malformation.

1:52

Now, we do see CSF slightly prominent

1:55

in the folia of both cerebellar hemispheres.

1:57

And in a child with chronic anti-epileptic medications,

2:01

you sometimes can see that.

2:03

But that's not an intrinsic

2:05

developmental abnormality.

2:06

So, this patient does not have

2:08

an intrinsic developmental abnormality.

2:10

Therefore, there's no need to do a genetic

2:13

workup for a cerebellar malformation.

2:17

This is a retrovermian and

2:20

infravermian arachnoid cyst.