Practical Approaches to Fetal CNS Evaluation - SD

Introduction

My name is Ellan Timor.

At times you will see my name appear as Elon Timor Trich,
which was my name
before I added the name Timor.

I work at New York University in Manhattan,
and I am the director
of OBG yn Ultrasound in the department of
obstetrics and gynecology.

I worked there for the last 10 years,
and I also worked
at least
12 years at Columbia Presbyterian in Manhattan.

I think that you will enjoy
the slight presentation that I put together
in addressing the fetal brain,
normal and pathological fetal brain.

I consider scanning the fetal brain an integral
part of an anatomy scan.

I also think that we have to
scan a little more than what is mandated today,
namely the axial planes using the transabdominal scan.

You will see in my lecture that I place a
heavy weight on trying to get a coronal plane
and a sagittal plane, namely the midline or
median plane of the brain.

This way we can really
give a thorough examination of the fetal brain.

In this lecture, I would like to
talk about practical approaches to the evaluation
of this fetal central nervous system.

First Trimester Embryology

Before I get to the mature
fetal brain, let me talk a little bit about the first
trimester, and I would like
to review the developmental embryology using 3D ultrasound.

If you scan a
an eight week, eight week one day
embryo
with a high frequency transducer, you are able to see
quite a large number
of brain structures at this early gestational age.

Some of these are seen in this slide,
and you can recognize that
string of sonar lucencies
that make up the convoluted
primitive
brain ventricles of this embryo.

You can again see the cephalon,
the mesencephalon,
and the area of the east most, a very narrow passage between
the fourth ventry, the future fraud force vanco,
which is the cephalon and the mesencephalon,
and that is the aqueduct of Sylvia.

If a 3D acquisition
is done on such an early embryo at eight weeks
and one days, you can see the median axial
and coronal displays of this
fetus, this embryo containing the brain.

If you then invert
the fluid field areas, you can
transform them in from an koic into a
an echogenic structure, which then
represents the string of ventricles,
almost like a cast of these
primitive fluid field
structures in the embryonic brain here.

Now you see in the lower right part
of the slide, an anterior view
of this inverted ventricular system.

I draw your attention to the interhemispheric foramina
of Monroe, which will be later important to this,
distinguish it with from pathologies,
just putting together the lateral in the frontal view.

Please realize that a large number
of embryonic structures can be seen at this early age.

Several articles were in the literature
that we're capitalizing on these views
to diagnose a normal brain
as well as several pathologists
of the brain at nine weeks and two days.

The ventricles change somewhat,
and you can see the posterior horns
that on the lower superior view
that they are more developed.

The cephalon is getting progressively
relatively smaller on the expense of the lateral ventricles
that are in the hemispheres.

So 10 weeks and four days.
Again, the rhombin cephalon is a little smaller
compared to the lateral ventricles of the hemispheres,
and you can see the imprint of the Cate Plexus at 11 weeks
and one day, almost the same is seen again,
the relationships change.

If you then scrutinize this composite slide
from seven weeks and six days to 11 weeks
and one day, looking at the later frontal
and superior views, you can see that
the tele cephalic vesicles, which are being mainly the
frontal horns are much smaller
than at 11 weeks on the expense of the
roen cephalon, which becomes relatively small.

So this is a natural development
of the embryonic fetal brain where the hemispheres are increasing in size
and posterior fossa, the cerebellum
and so forth are relatively smaller.

Now, where can this be of any clinical importance?

Here is a semi lobar ceria at nine weeks
and two days in which please pay attention
to the fuse, the anterior horns
that are seen on the two dimensional as well, on the
on the inverted image of the anterior horn.

When you compare it to the normal, you can see
that in the normal case, the f comes in between
and separates the two anterior horns.

On the right picture,
you see the fused anterior horns.

This is clearly evident on the tonal planes
in the upper part, the fuse, the anterior horns
and the inversion of the
ventricles in the lower part and circuit.

A little later at 10 weeks, a semi lobar hollow pro is shown
with inversion rendering,
and again, all what you see is fluid inverted.

In the lower picture, you see the imprint
of the far in all three.

You can see the fused anterior horns later on in 13 weeks.

This is now an all lobar hollow protein celi in which
there is no separation between the lateral ventricles.

You see that there is no imprint of the facts on.

When you look at the on the superior view
here is at 14 weeks, five days, again, a semi lobar
in which the anterior horns are fused,
and the posterior horns are separated by the imprint
of the Fs on the upper left and the upper right pictures.

The composite picture shows the same again for comparison.

Second and Third Trimester

Now we turn to the second and third trimester,
and there are guidelines
of performing the basic examination and
the fetal neuro sonogram published in the ultrasound in
obstetrics and gynecology in 2007.

This issue of the Y Journal describes the basic and the target, the neuro scan.

Here you see the three axial planes that are generated by
a transabdominal probe,
the trans ventricular plane on the upper picture,
the trans thalamic plane, of course, as the name implies,
cutting through the two thalami
and the slightly posteriorly slanted
cere plane, which develops much in much more detail.

The posterior phos with the two cerebral hemispheres,
the cisterna mag,
and this we see a little bit later, the vermes.

The basic brain scan has to contain in addition
to all the biometry that is common knowledge.

Also the following brain structures, the head shape,
lateral ventricles, the calve, septic lucidity, flanked
by the two walls, the thalami, the cerebellum,
the cisterna magna, and the upper spine.

Here is the trans ventricular plane again,
on which you see the frontal horns, the cave septic pellucid
between the two lateral walls, the posterior horns
with the cate plexus.

You can measure the atrium
of the lateral ventricle, preferably where it contains
cate plexus.

This, the trans thalamic plane again,
showing the frontal horns, the carbon cept pelus,
the two lateral walls of it, the FX in the anterior part,
the ami on the two sides,
and the hypo capal gyrus.

In this area, you of course measure the VPD,
the head circumference
and the occipital horizontal distance.

The cere plane, which I said is a slightly slanted
axial plane, will highlight the cerebellum
you seen here, the cy magna,
and the vermes.

However, this is not exactly the best image to
prove that there is a ver is you can measure all the
important measurements on this plane.

Targeted Fetal Neurosonogram

Now, if an abnormality is detected during the basic scan,
we then go and do a detailed
or targeted fetal neuro sonogram, which is recommended.

This is almost equal to a multiplayer imaging,
which is based on 3D.

This scan looks at the brain in greater details
and adds to the axial plane.

Also, the coronal
and the sagittal planes, which are then included.

It can be performed transabdominally,
and if possible, the first
ver the fetuses in vertex presentation,
then preferably transvaginal using 2D
or 3D sonography.

We add, as I said,
the coronal sagittal planes,
and in this case, all the sections radiate from one point,
which is usually the anterior al
as you can see it.

In this picture, we sneak into the fetal brain
through the openings between the cranial bones.

This slide demonstrates the major avenues into the fetal brain, the windows, so to say,
the anterior frontal, the sagittal sutures,
the atopic suture, the anterolateral, squamosal,
and posterior lateral fonts.

The last three enable us to try
to sneak into the posterior FoST to see them much better.

The lambda suture is also used sometimes, but rarely,
and these sutures, of course, close as pregnancy progresses.

The suggestions for a transvaginal
or transabdominal sonography as far as the coronal
and sagittal planes are concerned have
to contain the brain structures de delineated here, the
anterior and posterior horns, the third
and fourth ventricle, the interventricular forin, also known
as Monroe, the ca septi pelus verge.

As you will see later, the corpus scum with its parts,
the perusal artery
and the sum of the nuclei, the thalami, the ak nuclei,
and then the posterior pho with the cerebellum, the vermis,
magna interhemispheric fi fisure,
and later on the gyri and salsa.

The ocular scan.

Coronal Sections

Here are some of the coronal sections displayed in a view to better understand a frontal,
a mid coronal anterior, mid coronal section,
a posterior midal and a posterior occipital section.

Here they are detailed.

The frontal two
or trans frontal plane contains the interhemispheric fisure
and the anterior horns.

They're not peek through on this picture,
but you will see them on the next one right here.

These are the anterior horns.

This is though a mid coronal
or trans cow, that plane going through the cow, that nucleus
that is seen under the lateral ventricles.

You see the ca s with the two membranes separating it from the anterior, the frontal horns.

Here is an occipital ceal plane showing clearly the occipital horns.

Rarely will they be totally symmetrical In this case.

There is a slight asymmetry, which is normal.

You see the interhemispheric fisure, the incipient gyration and ation of the brain.

You see the cerebellar hemispheres, and you see the vermes
and the cisterna magna.

Median Plane

No detailed fetal neuro sonogram is completed without seeing a median plane.

Median plane is on, is the single plane that runs through the midline.

There are many sagittal sections with only one median plane.

Some people call it mid sagittal mistaken term,
but widely used on this.

You can see clearly the structures
that are essential to a scan whether the brain is normal
or suspected for abnormality in a detailed fashion.

Here is the median plane in which you see the corpus callo,
the ca pellucid, the brain stem,
very important to examine the ponds.

The posterior fossa with the in the median plane
of the ver is the fourth ventricle, the cisterna ambience above the cerebellum.

The cisterna magna behind
and below the cerebellum at 16 weeks.

Don't look for the corpus scum
because it is not yet developed at 22 weeks,
however you see it in its full beauty.

Below is the car septic lucidity.

Here you see the anatomy enlarged,
and in more detail, the corpus callosum is
not the bright echo above it,
but the koic echo below the echogenic line.

Here is the beak, the rum, the knee, the nu,
the body or the corpus, the splenium
or the tail, which drops down almost
to the quadri germinal plate,
and that is how you should consider it fully developed.

Reaching that milestone be below is the cave septi,
and the posterior part
of this cave stipul is called the cave verge.

At times, it's large.

This is not part of the ventricular system.

They are isolated structures that
regress almost totally towards delivery.

And in early infancy, this was a 22 week scan,
a 34 weeks, the corpus scum is seen.

The CAEP is smaller, no carbon verge is seen,
but the duration
and the ation of the brain is almost complete.

Turning on the color, you can see the anterior cerebral artery that branches into a
so colors of marginal artery and the
and the peric colossal artery.

You can see it with regular color,
but the best is with power.

Doppler has bigger sensitivity,
and it attests to the fact
that the corpus callos is present.

I will talk about that somewhat later.

To emphasize this point,
no thoro fetal neuro scan is complete without displaying the
median plane to scrutinize the corpus
callosum and the vermes.

On this slide, the oblique
or para sagittal plane is displayed,
and you can see here the entire lateral ventricle
with the choroid plexus.

The anterior part of it is called teleco.

There you would look for a grade one bleeder under this area
in the thalamus, anterior horn, posterior horn,
and at times also the inferior horn.

However, that should really not be seen.

If you see Tula, if you see it clearly, think
of a dilatation.

Here is a an image of the cortical surface doing a median plane.

These were of course,
developed towards the end of the pregnancy.

It is a sagittal, as was a coronal plane of a normal
brain showing the gyre and the sal side that develop.

One more issue.

The insula is developing at the beginning at
around 20 weeks, which this is
only a small indentation is seen later on the temporal horn and the occipital horn are
covering it completely.

That's the reason that it's called,
it's called the island, or the insular.

Here is where you would look for the middle cerebral artery.

Three-Dimensional Ultrasound

Let's turn to three dimensional ultrasound,
which can be a subject
for navigating into the in the volume
and to perform multiplanar imaging.

You have a lot of displays,
but the difference between the 2D
and the 3D displays are that in 2D, the pictures
the sagittal pictures emanate from a central point
of the al and radiate out.

In 3D ultrasound,
after obtaining the volume, the display will have
all the planes parallel to each other, as in city or in MRI.

First of all, we select the region of interest
to obtain the volume.

Then depending on our equipment,
the scan head automatically acquires the volume,
the display, as far as I'm concerned, I like
to have it always like this,
because then you don't make mistakes in
identifying structures or sides.

The coronal is in box A, the sagittal is in box B
with the fetus looking to the left,
and the axial is on box three
with the occiput looking upwards, right
and left are as in the in the
in the radiographic pictures.

Then the question is what you do with the volume,
how you get most information out,
and what display modalities you will use.

The first display modality will be, of course,
the orthogonal plane in which you can then use the
navigation with the marker dot.

You can then use the six slice in tomographic
or in orthogonal plane display.

You can look for vessels or in tomographic
or angiographic three display in the orthogonal planes.

You can do inversions.

You can look for volumes of the fetal brain.

All these are the ways to look at fetal brain.

So let's start with the multiplayer imaging.

Here I display them in box A, coronal box B,
sagittal box C, axial.

These are projections, which are at right angles
to each other, and you can study them simultaneously.

Here is a little exercise in taking the marker dot
with your cursor
and go into the different parts of the brain.

In this case, this is a pathology with a cephalic.

You see that I'm dragging the marker dot
all three dots in all three boxes
indicate the same exact plane.

Here, for instance, I am in the area of the midbrain.

Soon I will put it on the vessel here,
and you will see the vessel in all three projections.

Volume contrast imaging is a possibility,
and you can see here
that the slice thickness can be varied from about one
to almost 15 millimeters.

Depending on that, you will see a better
outline of the structure.

Here is a very thin slice,
and the previous was a very thick slice of it.

You can also display the brain in a
in a way that is displayed in MRI
or ct, serial consecutive
coronal pictures taken along the lines
that are on the scout picture, which is a sal display.

Here is a coronal display,
and all the other pictures are along the lines here.

Of course, this is the median plane with the corpus scum.

On the upper one, you see the right vent, the right lateral ventricle.

On this one, the left lateral ventricle.

If you turn on color on the orthogonal planes,
you can see the middle cerebral artery
and the most important one,
the peric colossal artery, which is seen here.

You can then strip the volume from all the soft tissues,
and you can display it in this modality,
or which is only the color angiogram
or the glass body with the outlines of the fetal brain.

In this clip, you can see a color acquisition was done,
and here the SAG is displayed in box A as you see, and tweaking
and moving the vol, the
head into the positions that will present a
complete and perfect median plane.

We will look at the median plane here, displaying
the perusal artery and other arteries.

The simplicity of this is really remarkable,
displaying the vasculature of the brain in the angiographic mode,
you can employ the ine display.

This is excellent for teaching
and studying the different structures of the brain.

Excessive fetal movement will result in poor quality
volumes, which in its stern will result in artifacts.

Here is, for instance, a picture that was acquired while the fetus was moving.

Please discard these.

Don't try to analyze them
because you will give raise to a lot of unnecessary anxiety.

Here is a sixth slice display again, the
selected area, which is this displayed here,
is collapsed into a 2D image to enhance the borders of it.

It is most useful when you have pathological findings.

In this clip, you
I display how I scan the brain in the axial
fashion in the lower right box.

Following that will be a sweep in from ear
to ear in the sagittal plane,
displaying the lateral ventricles, as you see right now,
or the midline right now with the corpus callosum.

The other side, the brain ventricles here are,
here is a borderline ventriculomegaly, the right
1.2 centimeters.

The left one, one centimeter
that are displayed in six slides.

Inversion is a cast renders a cast like appearance
to the fluid filling the lateral ventricles.

This was all suggested many
many years ago in 1959 by day
who filled the lateral ventricles with wax
showing them as displayed here at 12, 18 and 32 weeks.

We do the same right now just by doing an inversion
of the fluid field.

Lateral ventricles here, for instance,
is an arnal Chiari malformation.

In the next slide, you see the fluid
that was found in the lateral ventricles.

I will point out when it turns,
and I'm stopping it here, the dilated third ventricle,
which clearly shows that this is a
an obstructive hydrocephaly
probably at the level of the of the
aquit of Sylvia.

You can measure brain volumes by outlining in a successive fashion, the turning
volume of the brain.

This can be used
to determine also gestational age if it's done correctly.

It is a clip outlining the acquisition of the brain volume.

The posterior fossa is shown on this clip.

The acquisition was done in box B.

You turned the head into a coronal plane in the box A
into an occipital op.

In box B now is clearly seen the sagittal plane
enlarging the picture
and the concentrating on the posterior fossa, the dot,
the marker that is put on the vermes.

In all three, you will see the display of the vermes
going to a six slice.

We emphasize the finding you, we can measure the
cerebellar diameter, the cag,
then the nuclear translucency enlarging the picture.

The measurements can be done much more in a much more precise way.

Here is the widths of the cerebellum.

In the next measurement, you see the height of the
cerebellum.

In addition to that, you can measure the
cisterna magna right here measured.

If the picture is crisp enough, you can also relate
to the CLE fold
and measure it in this on this picture.

Clinical Examples

Several clinical examples.

Now, one is of an agen of the corpus scum,
showing you the difference between 2D and 3D di diagnostics.

Here is the corpus celi with an 1.1 centimeter posterior horn,
and the several sections
that can be obtained showing several structure
structural anomalies like the FX is
dipping down into the third ventricle.

There is dilatation
of the ventricles dangling choroid plexus.

There is no cross section of the corpus coo
that would be in this particular place.

On the sagittal sections, there is a total lack of
the corpus coo.

The peric callosal artery is not seen as a normal structure.

There are different ab aberrant vessels,
however, watch the simplicity of it on a 3D orthogonal
multiplayer set of pictures.

Here are some of the indirect signs, widely separated,
vertically oriented lateral ventricles.

The Viking helmet sign, as you see it here,
and the interhemispheric fissure that
that meets the third ventricle.

The other in sign is colpocephaly,
which is the dilated posterior horns.

They also look like teardrops,
should you reverse the direction of them.

They are also parallel to each other.

If you do an inversion of the fluid inside,
this is what you would see.

Again, it should be clear that the colpocephaly in here,
the anterior horns seem almost normal,
and they are parallel to each other.

Indirect signs are also the radial gyre
and salsa on the median surface,
which is called the sun birth side.

Be advised that you only see it when the salsa
and gyre develop on at around 28
to 32 weeks.

The only direct signs
that you see on the medial plane are the corpus collo,
the lack, the missing corpus collo, the ca, septi, pellucid,
and the perusal artery.

These are missing.

This I call the triad that has to be present in order
to have a normal corpus scum.

Here is another example of the absent corpus scum, absent
singular gyrus above it
and the sunburst appearance of the gyre.

Another case, 24-year-old lady, G three P one,
previous term pregnancy ultrasound at 20 weeks was red at
normal at 28 weeks was red at cephalic.

Transabdominal scan shows definitely
that it does not look a normal trans
thalamic and transce plane.

The sagittal sections in the midline
look almost normal.

Even the cerebellum is seen.

The fourth ventricle is somewhat pressed anteriorly by a fluid field structure in the back,
which also shows on the coronal scan.

If we are watching this clip,
you can clearly see that there is a large fluid field area,
but when you go anteriorly, the
ver is is clearly seen.

Here is the bay of the fluid field area.

Going back here is the ver is again perfectly normal.

This structure was read
as an arachnoid cyst.

The question is, would you order a fetal MRI
and that this point, I don't think it is really necessary.

I will be talking about the use of MRI In subsequent slides.

The ultrasound really established the diagnosis.

The cyst wall was seen,
the normal fourth ventricle was seen.

The tentorium
and the tor is minimally elevated
and the hemispheres are displaced toward the anterior,
the cl, the clus and upward.

The neonatal scan is showed here clearly
resembles or almost similar to the antenatal scan.

Here. You can see clearly the cyst wall in this area.

Of course, an MRI was done
after the delivery, which reinforced the finding exactly
as you saw it in ultrasound.

The neonate had a shunt placed.

The shunt was removed at two months of age due to infection.

However, the size
of the ventricle had stabilized, remained normal.

At six months,
it's achieved all developmental milestone.

This baby now is more than one year, one year
and two months, and is developing normally.

So neurosurgery called it an arachnoid cyst.

The MRI called it a mega cyst
and a mag versus an arachnoid cyst.

Here is another patient who is 42 years old, referred
for a second opinion anatomy scan for brain anomaly.

The family in obstetric history were unremarkable.

On this transabdominal 2D picture, not too much was seen on the coronal sections.

However, he saw a large subarachnoid patient dilated occipital hearts, mainly one of them.

The midline looked normal.

The one side, the right side looked pathological to us.

The question is, again,
do you need an MI at this point?

I think that before you do that, you have
to really explore the possibilities
by the three dimensional technique.

Watch this clip.

I'm going from inside the ventricle
and go outside the subarachnoid space.

Also shown on all of these, go back into the ventricle,
grab now the dot again from the ventricle into the
subarachnoid space, clearly shown by the other two pictures.

Here again, going inside the ventricle scene on A and C
and go and wandering outside into the subarachnoid space.

So clearly there is a connection with a posterior horn
to the subarachnoid space.

Seen clearly on this pictures right here,
the arrows show at this connection inverting it.

You already saw that.

I like the inversion mode
because it gives me quite a nice three dimensional view.

You can see on this moving clip the connection between one of the lateral ventricles.

This is the normal ventricle not connecting
with the subarachnoid space, however, this one does.

That's the fluid in the subarachnoid space.

Here the annotations on it,
left lateral ventricle, left right lateral the connection,
the site of the cleft with a subarachnoid place.

So here are the differential diagnosis.

Of course, this was a schizo cephalic.

When we look at the MRI, it definitely
confirms the diagnosis nicely.

You can see here the comparison
with ultrasound in exactly the same planes.

Here is the cleft shown by ultrasound
and MRI ultrasound again, the cleft here,
MRI cleft.

Here in with MRI.

So it's a unilateral right occipital open lip ce
where the subarachnoid space communicates
with the posterior aspect of the right lateral ventricle.

Schizo cephalic can be unilateral
and bilateral, it can be closed lip and open lip.

Here you have a diagram of the four possibilities.

Here is a closed lissencephaly with a unilateral
and bilateral cleft.

Here you have an open lip, schizo, cephalic, unilateral
and bilateral.

The next case, and probably the last one is a 33-year-old G
one P zero referred
for second opinion anatomy scan for a brain mass.

Family and optical history were unremarkable.

The horizontal axial pictures are almost unremarkable,
but if you look closely,
there is a fluid fill area in the posterior fossa,
and there is a hyper coic nodule in the
in the posterior area of the posterior fossa.

The sagittal picture shows exactly the same.

We watch this enlarged
during our observations from 20 weeks to 22 weeks.

You can see here a three dimensional picture.

Now the fluid field space is much larger.

The echogenic area is right there.

The of the same size tomographic
ultrasound images were done.

You should always do them in order to see much better the anatomy.

In subsequent slices, again, horizontal sagittal pictures,
which clearly show the pathology.

The in utero diagnosis was a thrombus
of the dural sinus involving the to phi
or the confluence of the sinuses.

The reason for this may be
that here four large draining veins meet
and are creating
a slowing of the blood flow, which then may give raise
to thrombus formation.

Here are the fetal MRIs, again, exactly the same picture
that we obtained with transvaginal ultrasound.

Looking at the fetal brain, here is though the last case,
which was referred for second opinion for a brain anomaly.

Now that you already have seen a similar case,
I would like to draw your attention to the fact that in this case also the transabdominal sonography 30 weeks
almost makes the diagnosis
because you see here a large cleft opening on one side
and maybe even on the other side.

Again, the coronal sections are IM important, doing them
by transvaginal scan.

The midline looked normal to us.

However, some suggested that maybe there is a thinning
of the corpus scone that may be the case.

Tomographic images are important
to look at them and hear.

Again, the bilateral clefts are pretty obvious on most of the planes.

3D inversion was again done by me,
and they confirmed on the the
cleft on one side there was not enough well delineated fluid on the other one.

So even inversion has some drawbacks.

But on MRI, you see the bilateral cleft
here are the coronal planes.

So it's bilateral open lip skins and celi.

Conclusion

Let me sum up and make, draw some conclusions.

Transvaginal, transabdominal 2D
and 3D fetal narrow scan is feasible
and definitely here to stay.

The most important task is to reassure the mother
or the couple of a normal developing brain,
and that you can do in an elegant way with 2D
and 3D transabdominal and transvaginal scans.

The second important task is to precisely
diagnose the pathology for proper counseling and management.

Let me just say that it is extremely important
to invite the fetal
or the neonatal neurosurgeon rather to sit in at these counseling sessions
because they can meaningfully counsel the patient
before the baby is born, not waiting for the neonatal imaging studies to be done.

New technologies helped help in obtaining more detailed
and precise diagnosis to the d and 3D.

Ultrasound should be the first line diagnostic tool
to image the normal pathological fetal brain.

Mr should be used in selected
and rare cases to confirm the ultrasound diagnosis
before 22 weeks,
and they definitely can be used later on when the cortex
develops and when we expect to see heterotopia
and pathologies in the white matter in which MRI provides a much better picture than ultrasound.

Thank you for your attention
and I hope that I helped you
gain an insight in the fetal brain scanned by ultrasound.