The Fetal Head - SD

Introduction

Hi there, I'm Dr. John McGahn. I'm the director of ultrasound and abdominal imaging from the University of California Davis.

Our hospital isn't in Davis, California, but actually in Sacramento, California.

I've been there for over close to 30 years.

Now I'm gonna talk to you on a topic about ultrasound and the fetal head.

So I'd like to get started with my topic.

I'm gonna talk to you today on ultrasound of the fetal head.

Lot of different portions to talk on here.

We could talk upon ventricular measurements, etiology of ventricular magaly, ventricular cysts, vascular malformation.

However, I'm gonna stop at that point.

I'm not gonna talk about the posterior fossa.

So what we're gonna talk about is mainly the supratentorial fetal brain.

Ventricular Measurements

First topic I like to talk about is ventricular measurements.

There's a rule out there, it's the 10 millimeter rule.

I'd like to go back and talk a little bit about how that 10 millimeter rule got started and basically what this 10 millimeter rule means.

First publication on the width of the lateral ventricle was done by Cardozo out of San Francisco and he came up looking at the atrium of the lateral ventricle.

So he would look at that atrium came up with a hundred fetuses, had a mean of 7.6 millimeters throughout pregnancy with a standard deviation of 0.6 millimeters.

This is fairly interesting because what he did, instead of taking two standard deviations as many individuals do, he took four standard deviations and came up with a value of the upper limits of normal, of the ventricular atrium of 10 millimeters.

But in fact, like most studies do, if he would've taken only two standard deviations, he would've come up with a measurement of nine millimeters.

Second study that came out, and there were a couple other studies that came out was done out of our institution.

We did our study a little bit different.

Instead of taking a hundred consecutive fetuses, we took 500 fetuses that were examined by sonographers.

So these are a different pool of individuals that looked at the fetal head.

Our mean was a little lower at 6.6 millimeters, but our standard deviation was a little higher At 1.4 millimeters, we picked 2.5 standard deviations from that mean to pick our upper limits of normal, and we came up with the exact same measurement of 10 millimeters.

However, just imagine for a moment we would've taken four standard deviations and we would've had a value for the upper limits of normal of the width of the atrial fetal ventricle atrial of 12 millimeters.

So what would've happened if somebody would've gone ahead and we established instead of 10 millimeters, a rule of nine millimeters or 12 millimeters?

First of all, I'd like to emphasize that no one value separates the normal population on the left from the abnormal population on the right.

So if we pick 10, that does not completely separate these populations.

In fact, if we look at this, these populations do in fact overlap.

So there's no doubt the width of the lateral ventricle of some abnormals may be nine.

While some of the normals may go above that, well what would've happened if we decreased our upper limits of normal to nine millimeters?

Certainly we would've increased our sensitivity by minor increased detection of abnormals.

However, this would be at the cost of decreased specificity and what we do is we'd have major inclusion of normal fetuses.

If you look at different series, certainly this would cause a lot of maternal and paternal anxiety.

And in certain series where there is very mild ventricular magaly, this could lead to termination of a completely normal fetus.

What would happen if we increased our upper limbus and normals to 12 millimeters?

If we would accept four standard deviations, as in our study, well certainly our sensitivity would have decreased.

So there's certain abnormals that potentially we would have missed.

However, we would've increased our specificity.

So certainly we would have decreased the inclusion of a number of normals.

Well, let's look for a moment really what ventricular magaly means, especially at that borderline ventricular magaly between 10 and 12 or between 10 and 15.

If we look at isolated vi, borderline ventricular magaly in which there's no other abnormality detected in the fetus, we see and we stratify these between 10 and 12 and then between 12 and 15 we see that as the ventricles get bigger, the abnormal outcome increases.

So it's 9% and those ventricles from 10 to 12 and abnormal outcome was increased to 24%.

So as the ventricles get bigger in the second trimester, certainly there is increased rate of abnormal outcome.

Now a couple of questions I have.

Do male fetuses have bigger brains than female fetuses?

Second question. Do all males think they do have bigger brains?

And third question, do male fetuses actually have bigger ventricle than female fetuses?

Well, the answers to the first is no.

The answer to the second is definitely yes, but the answer to the third is very interesting.

In fact, if we look at male fetuses, they do tend to have slightly larger ventricles than female fetuses.

So what does that mean? Well, what it translates into is the rate of abnormal outcome with borderline ventricular magaly is greater in female fetuses as compared to male fetuses.

So if you have a male with a ventricle of 12 millimeters, that may in fact be more likely to be normal than if you have a female fetus with a ventricle of 12 millimeters.

And in fact, in this study, if you looked at that, the rate was 5% for males with an abnormal outcome compared to 24% in females with an abnormal outcome.

Pitfalls in Measuring Ventricles

Well, let's look at several pitfalls in looking at the ventricles.

First pitfall is the upside ventricle.

Now just think of any study that we would do and we'd only look at one half of whatever anatomical structure we're looking at.

So in the case of the fetal brain, most of the time unless that fetus flips, we're only looking at that downside ventricle.

Well back in 1990 and a couple of papers after that, they developed Myron and one of our sonographers outta uc. Davis developed a technique for looking at that upside ventricle.

If you angle the transducer through this thinnest portion or the temporal portion of the bone, you'll be able to see that upside ventricle.

It looks a little bit different, but what we found when we did another study on 500 fetuses, about 1% of the time we detected things on the upside ventricle or the upside cerebral hemisphere that we did not detect with detect with a normal view.

So normal view seen on the left and we do our angled view and we identify a large cyst that was invisible with our routine shot of the fetal head.

Another pitfall.

In fact, if you look at the fetal cerebral ventricles or the fetal head at one point in time, say that 20 weeks, you really need to look at that ventricle later on if in fact you're gonna reexamine that fetus for fetal weight because the ventricles are very dynamic.

If in fact you have a ventricle that's 12 millimeters, usually it decreases.

But on occasion they certainly increase.

And even if you do have a normal size ventricle, you should always look at that ventricle later in pregnancy.

Such a case posterior fossa looks pretty good shot of the fetal ventricle.

This is at 20 weeks that ventricle measures seven millimeters.

Nobody here would probably advocate a follow-up.

However, 36 weeks, this is the same fetus.

We see the ultrasound in the fetal head, a sagittal view of the fetal head.

MRI postnatally another MRIT one weighted postnatal and this turned out to be aqueduct stenosis.

In fact, we gathered several very interesting cases in which during the second trimester or early in pregnancy the fetal brain, the fetal ventricles looked normal, but later on in pregnancy they turned out to be abnormal.

These are six of these different cases.

Two of them turned out to be normal at 20 weeks.

The one I showed you later turned out to be aqueduct stenosis.

Three of them turned out to be hemorrhage later in pregnancy.

One case turned out to be normal early in pregnancy later on was porn cephalic.

I'll show you a couple of these cases during my talk.

Here's another potential pitfall.

What is the diagnosis here in this 14 week fetus certainly looks like this may be a dilated ventricle, but what we look for is we look, in this case there is no dangling choroid plexus.

We get a hypo coic cerebra and we see a line here probably corresponding to the subarachnoid space.

This is so-called pseudo hydrocephalus. Here's another case.

We're looking at the ventricle.

We have it measured, but you look at this other hypo coic structure, which is a cerebral, but we can identify this is pseudo hydrocephalus because we note the ventricular walls here, the upper, the lower ventricular wall.

We note again there is no dangling choroid.

Etiologies of Ventriculomegaly

Well finally, after just talking about the ventricular measurements, let's go on to particular etiologies of ventricular magaly.

When we talk about ventricular magaly, what we're really talking about the ventricles are enlarged.

It really doesn't tell us the specific etiology.

So there may be an obstructive phenomena such as hydrocephalus.

There may be male development or there may be a destructive order of the brain in which the ventricles do enlarge.

If we have massive CSF collections, it looks like there's large ventricles.

You think of three things.

One is a massive obstructive hydrocephalus.

The other would be a low bar holo pro celi.

The third would be hydrocephaly.

Let's take for a moment and separate out these three separate entities.

Entity number one, we look here we have a midline fes.

We look these are two separate cases.

One's more severe than the other. We look at the case.

On the bottom we see there's dangling choroid and we look here dangling choroid, we have cerebral tissue.

There was a normal face.

This is a case of two cases of hydrocephalus US

case number two, abnormal face.

Over here on the downside with a midline cleft, there is a mono ventricular cavity and what we also see there is fused thalami.

This is a lobar holo pros celi.

A low bar holo pron celi almost always is associated with a very dismal prognosis.

Has associated facial abnormalities and is often associated with trisomy 13.

The final entity here we take a look at, we see a midline fess, we see no cerebral tissue.

There was a normal face and this is hydrocephaly.

This is probably secondary to bilateral internal carotid artery infarcts and or contusions.

We also note the thalami are there, but they tend to be separate rather than fuse.

As with a low bar holo, pro cephalic, well things are never as simple as they they seem and there's often other more complex abnormalities.

Let's just take for a moment hydrocephalus and there's a number of different etiologies.

We do not have time to go through all these, but we'll take for a moment and look at a few.

Here's such a case where we have three separate portions.

The head on the left that shows ventriculomegaly.

Over on the right upper hand slide we show the posterior fossa that looks compressed or small and then we have a shot, the third image on the bottom through the spine.

This is so-called lemon head banana type deformity associated with Keri two.

So when we do an ultrasound, we go ahead and we do a complete evaluation and often we can come up for a specific diagnosis as in this case.

Other etiologies could include a large CI sternum magna, whether it be from arachnoid cysts, whether it be from Danny Walker Complex, which has a lot of variabilities from just minor inferior verian agenesis to this dandy walker malformation.

These could be potential etiologies of hydrocephalus.

This is an MRI and in this case there's severe cerebellar hypoplasia in this case as well as as a verian agenesis.

Maldevelopment

Next let's talk about male development as an etiology of ventricular magaly ally.

First we look here anterior posterior of this fetal head.

We look and we have copal cephalic, but we also look that the ventricle is parallel to the midline.

The frontal horn is not dilated at all and there is a prominent inner hemispheric fisure.

This is what a normal fetal head MRI looks like.

I like you to look for a moment and look at where that frontal horn lies.

Look at the trigon, it's barely dilated.

Now take the case that I just showed you and what you have is colpocephaly.

You have three parallel lines and this is a case of a genesis of the Corpus Col.

This ventricle has often been termed the teardrop ventricle.

If we took this cartoon in the face, put it on its side, we can see the teardrop ventricle both on ultrasound and looks identical on MRI.

This is the teardrop ventricle with that ventricle being parallel to the midline In a genesis of the corpus collo, once we see one abnormality, it's important to make sure that we can come up with a specific diagnosis.

So in this case, we went ahead, we did MRI, this is a T two 80 image and what you see is behind the orbit, another cyst.

So you see the orbit in front as a cystic structure, but you see a cyst behind that.

This newborn MRI again showed this large orbital cyst that called proptosis of that eye.

Here's a gross image of that showing the proptosis of one eye.

This turned out to be a Cari syndrome that we could diagnose by ultrasound.

A genesis of the corpus callosum often associated with choal retinopathy, mental retardations and only a few cases.

But if you see genesis of the corpus coum, think of other syndromes as in this case here.

Next I talked to you about ho LoPro and celi, but I only showed you the most severe form of a lobar holo cephalic.

There are other forms, the face predicts the eyes and before we had ultrasound, pathologists would look at the face and say whatever the face had would predict or the face would predict the brain.

So if they took a look at the face and it would predict what the brain shows.

So the eyes are really key here.

So if there is opia midline cleft, there is a huge probos that often was associated with some type of holo pron celi.

This is a case of a mono ventricular cavity associated with a cleft lip.

This is not as severe as the a lobar type of holo pron celi, but this is semi lobar holo proin ly prognosis is also very poor, often associated as well with trisomy 13.

An abnormality that may be missed in utero unless we look at the region of the cavem is low bar holo pros. Celi also called septal optic dysplasia.

In this entity we have fusion of the frontal horns and we have absence of the cavem septum.

Sometimes they may have visual impairment in these cases or developmental delayed.

So look very carefully for the region of the cavem.

If you get a squared appearance up here with pointed frontal horns, think of lobar holo, pro cephalic or septal optic dysplasia.

Destructive Phenomena

Well finally under ventricular magaly, let's move on and look.

Let's look on to destructive phenomena within the brain.

Here's a case of ultrasound here in which there is ventricular magaly, but there's echogenic material around the ventricular walls.

This is a CMV infection.

You can see the postnatal CT in which you see calcifications surrounding the ventricular wall and it's actually the brain destruction in which causes a ventricular magaly.

This has been called hydrocephalus X vacu.

So that means the ventricles just occupy the space of the destroyed brain.

Often the head circumference in these cases will be normal.

Here's a case I'm gonna show you again a normal 20 week ultrasound.

This is the 34 week follow-up. Remember normal at 20 weeks.

This is the 34 week follow-up and what you see is a case of porn celi.

You see a large CSF collection that does communicate with the ventricle and it is thought to be due to some sort of cerebral artery or mine cerebral artery infarction.

You can see the posterior phos is normal.

The opposite side of the brain is normal.

This is a destructive phenomena of brain.

It may be difficult in utero with ultrasound alone to tell the difference between skis and celi and porn celi, but MRI in utero may be helpful to distinguish between these two entities.

In this case, postnatal MRI, we can see that there is on the side of the porn celi that there was a metal cerebral infarct.

We also note that the ventricular or ventricle is lined by white matter.

Ventricular Cysts

Well, we have two other topics to cover in terms of looking at the supratentorial brain.

Let's look at ventricular cysts.

I'm gonna give you two different cases, case A, case B, and I'm gonna actually show you case C.

So take for a moment.

19 week fetus, couple of cysts within the ventricle.

29 week fetus.

Looks like we may have a cyst or two in the downside ventricle and then another, let's say 29 week fetus, large cyst, maybe in the ventricle we can't come up or we don't really know.

So you have three separate cases, all different diagnosis.

So let's look at each three case, one 19 week fetus.

Everybody knows about this chor plexus cyst.

They're benign in themselves.

They occur one to 4%, they all resolve, or most of 'em resolve spontaneously.

But what you have to watch out for is trisomy 18.

So if you see this, be sure to check the biochemical markers and the serum of these patients as well as do a very comprehensive level two exam.

Looking at the hands, the feet, the heart.

In this case we go ahead and we looked at the hands.

They never opened or closed. They were very clenched.

We also looked at the heart.

It may be hard to appreciate this, but there was an AV canal and this case was a case of trisomy 18.

Now second case, case BI showed you doesn't look too much different, but this is at 29 weeks.

Choroid plexus is, most of them are resolved by this time.

This is in utero hemorrhage.

It's often spontaneous, occurs about 29 30 weeks.

Includes a number of different disorders that may cause this.

Sometimes we really cannot find a specific etiology for this.

And later on you may get obstructive hydrocephalus because of the obstructive phenomena of the hemorrhage, in these brains.

A couple other cases it's important to document.

These are about 30 weeks.

So you see a cyst here and these are cases of in-utero hemorrhage that finally developed into a cyst.

Finally, the large cyst I showed you is neither of those.

It in fact, here's the CT after delivery and this was an arachnoid cyst.

So it's basically an arachnoid line in which there's cells that secrete CSF and they get bigger and bigger and bigger.

They may have mass effect.

Usually they're not within the ventricles, but they're within the CSF cisterns antico.

They look rounded, can occur in the posterior SS sial brain is where they occur.

Vascular Abnormalities

So I've taken you through a list of different things and the last thing I'd like to talk to you about in the supratentorial brain is looking at vascular vascular abnormalities.

Next case we get a case here, we see sort of a tubular structure in the middle of the brain.

What do you do next?

Well, there's one or two things we can do.

Certainly one thing we can do is we can go ahead here.

We get an MRIT two weighted and what we identify is a signal void.

This indicates blood flow.

Well, what do we have with ultrasound?

We have power doppler doppler.

And in fact, you look here in power doppler, this is a vein again, Galen aneurysm.

It's really an arterial venous malformation.

These fetuses can develop hydro drops or after delivery.

They can end up with cardiac failure due to high output failure.

They sometimes develop hydrocephalus and they can be treated after delivery with different new endovascular techniques.

Second case, 18 week ultrasound on the left, just pointing out the cavem, the posterior FOSS on the left side by 30 weeks.

I did a follow-up ultrasound.

I actually did one in between at about 26 weeks.

The one at 18 weeks, 26 weeks was normal.

At 30 weeks, I see this large posterior fossa echogenic mass.

So what is it? Well, I came up with two things.

Could it be a tumor? Well, probably it doesn't have enough mass effect and it grew really fast in four weeks.

Or is it a hemorrhage?

Did an MRI decreased signal intensity in the two T two weighted MRI and what this happened to be is cerebellar hemorrhage.

Very rare to have cerebellar hemorrhage.

Usually you get it supratentorial and most of the hemorrhages are from the germinal matrix.

We really never found out the precise etiology.

This was evacuated and this fetus did well after that.

Alright, all right. Somebody's measuring up the ventricles in this case.

So take a look at that 12 millimeter ventricle.

Stop for a moment. This 20 week fetus, is this in fact being measured correctly?

Well look real closely because you see that choroid plexus.

It isn't dangling, is it?

So in fact, they're measuring the, almost the nearly entire cerebral cortex.

And if you remeasured it, there's something extra axial that's pushing the brain to the side.

We waited two weeks and the fetus flipped over.

And now that whatever it is is decreased in size or decreased in diameter from 12 down to 7.5, what do we do next?

We take a look at that. We do our MRIT two weighted image and in fact, we see this structure here on the T two weighted image.

And this also turns out to be hemorrhage.

This is a subdural hematoma in utero.

Subdural hematomas are rare, but they're not uncommon to occur in utero laundry list of different things.

Most of the time they're idiopathic can be secondary to trauma.

Other etiologies such as different coagulopathies, may be the etiologies of these hematomas.

These are important to diagnosis all other etiologies of hemorrhage in the fetus because they can occur with traumatic delivery.

But they may in these cases, they're not at all due to traumatic delivery.

They occurred spontaneously for other etiologies.

Conclusion

So what I've tried to do in the last 30 minutes is taking you through the supratentorial brain.

I've gone ahead and looked at the ventricular measurements, why we picked 10 millimeters, what in fact happens if we look at fetuses with 10 to 12 or 10 to 15 millimeters.

I've talked about different etiologies of ventricular magaly.

So there's a number of different etiologies of ventricular magaly from hydrocephalus to structural abnormalities, to mal development to actually destructive phenomena within the brain.

Shows you a couple of different examples of different cysts that are close or appear to be within the ventricle so you can be aware of some of these different mimics and then talk to you about other vascular anomalies that you may see within the fetal brain.

I've hoped you enjoyed this brief presentation, the supratentorial brain.

Thank you for your time.