0:01

This is a fetal ultrasound performed

0:03

at 29 weeks gestation,

0:05

and it shows profound ventriculomegaly.

0:08

We can actually see dangling choroid plexus.

0:11

And this was further characterized with fetal MR.

0:15

That fetal MR shows massive enlargement of

0:19

both lateral ventricles.

0:21

We scroll inferiorly.

0:24

The third ventricle is on the bigger side.

0:25

The fourth ventricle is not enlarged.

0:30

If we look at this sagittal image,

0:33

we see the massive enlargement

0:36

of the lateral ventricles.

0:38

There's enlargement of the third ventricle.

0:41

And if I zoom in,

0:44

I can actually see the superior aspect of

0:48

the aqueduct of sylvius looks patent.

0:50

We're not seeing it inferiorly.

0:53

And while this is a very small structure,

0:56

the fact that we have a tri ventricularmegaly,

0:59

both lateral ventricles and the third ventricle

1:02

without an abnormality of the fourth ventricle,

1:05

or at least without enlargement

1:06

of the fourth ventricle,

1:08

suggests that the aqueduct of Sylvius is a likely

1:12

location for an abnormality of CSF flow.

1:15

Now, there's another finding that we see.

1:18

The cerebellar vermis has an unusual configuration,

1:23

including an abnormal configuration of

1:27

the nondilated fourth ventricle.

1:29

If we look on this image,

1:32

we're actually in axial image of the posterior fossa.

1:35

We're not seeing a cerebellar vermis,

1:37

and we're seeing sort of a rounded appearance

1:40

of the posterior aspect of the cerebellum.

1:43

That, to me,

1:45

is suggestive of rhombencephalosynapsis.

1:48

Obviously,

1:49

we want to confirm this with postnatal imaging,

1:51

but this is suggestive of rhombencephalosynapsis.

1:54

And why does this make sense?

1:56

Well,

1:58

rhombencephalosynapsis can be associated with

2:03

a congenital aqueductal stenosis.

2:05

That congenital aqueductal stenosis is felt to be

2:08

related to abnormal transverse migration

2:12

of the inferior colliculi,

2:14

resulting in something that could be

2:16

referred to as mesencephalon synapses.

2:18

So in patients with aqueductal stenosis,

2:23

always pay attention to the cerebellar vermis,

2:25

and you may actually find that there's also

2:28

associated rhombocephalus synapses.

2:30

That may then

2:32

allow appropriate referral to genetics for

2:36

evaluation of other genetic abnormalities.