The Fetal Spine: Pearls & Pitfalls - SD

Introduction

I'm Dr. Beverly Coleman, professor of radiology at the University of Pennsylvania in Philadelphia, Pennsylvania, and I'm gonna talk today on the fetal spine Pearls and Pitfalls, the fetal spine, pearls and Pitfalls.

We'd like to begin discussing the pearls. There are very few pearls that begin with always, but in the evaluation of the fetal spine, it is important to always try to use more than one transducer. High frequency linear transducers are best to image the spinal cord. It is also important to always try to image in two planes longitudinal, either coronal or sagittal, and then the transverse or axial plane. The spine should be evaluated with the fetus in a prone position and with the spine away from the uterine wall.

Today we're going to cover the normal fetal spine. Miscellaneous anomalies pay most attention to neural tube defects. And finally, conclude with sacral coccygeal teratoma.

Normal Fetal Spine

This slide is an example of a normal spine visualized with a 12 megahertz high frequency probe with the fetus in a prone position. Notice that you can see the ossification centers for the two posterior arches, the spinal cord itself, and the ossification center for the body on the longitudinal view. Notice how the ossification centers line up such that the bony structures always extend inferiorly and narrow in the very distal part of the spine.

What we know about the ossification of the fetal spine is that the neural arch centers are most important and the pattern of ossification is variable. We don't know all there is about the cervical and thoracic patterns, but the lumbosacral spine pattern, we know ossified intercaudal direction every 16 weeks with one level at about two to three weeks until the L five to S one ossification centers are done.

We also know that the spinal cord with this conus medullaris typically ends at the L three level or higher, the conus medullaris, this is an example of the conus ending normally at about L two. Here is the conus ending at L three notice it has a sort of arrow shaped or flame shaped termination where it points to the level of L three. And here are two examples of low insertion at L three to four and here at L four to five.

Miscellaneous Spinal Anomalies

Now let's move on from normal anatomy or the beginning of this talk to miscellaneous spinal anomalies. And under this category, we are going to address abnormally shaped vertebrae, absent or dysplastic vertebrae and kyphosis and scoliosis.

Abnormally Shaped Vertebrae

This is an example of a patient referred for suspected spinal abnormality and notice that there is a single thoracic hemivertebra on these longitudinal clips, and you can see the ossification center that is off axis compared to the other ossification centers.

This is another subtle case where on the outside it was felt to represent an open spinal defect. And here we can see on both the clips and the still images that the posterior arch centers do not line up appropriately. The cord is deviated a little to one side and notice that these posterior arch centers do not oppose normally in the triangular shape. If you look at the longitudinal view, you can see the extra ossification and thickness and the malalignment related to this single isolated anomalous vertebra. At L one, it is possible to have numerous dysplastic and anomalous vertebrae.

Here is a fetus where the diagnosis was totally missed outside and none of the visualized ossification centers line up normally on the longitudinal view. Here's another example of a proven case of costochondral dysplasia, and on this clip you can see on the longitudinal view that there are numerous irregular ossification centers. We can see the abnormality on these fixed transverse views with the thickening and irregularity of the ribs, which do not align normally on a coronal view and a clear sort of wide spaced and divergent on this axial view.

Absent or Dysplastic Vertebrae

Large segments of the spine may be absent, and that happens most frequently in sacral agenesis cases where you can have totally absent vertebrae. This is a fetus that has an omphalocele and you can see the abdominal wall defect anteriorly as well as missing sacral vertebrae on this view at the level of the iliac crest, the conus medullaris ends low at approximately L five below the normal termination level of L three or above.

Kyphosis

Let's move on now to abnormal curvatures and kyphosis. The word kyphosis refers to abnormal forward angulation of the bony structures at greater than 40 to 45 degrees. This is usually caused by fused vertebrae that often are referred to as block vertebrae. It can also be associated with severe anomalies such as an open neural tube defect or spina bifida type case.

Here's an example of a case of sharp kyphosis, and we can see that there's almost a 90 degree angle with the osseous structures here on our 3D rendering. We notice that the spinal processes splay outwardly as we go more distally near the area of the sharp kyphosis. This fetus also had an abdominal wall defect with herniated bowel at the base of the cord and polydactyly. On this clip, you can see that there's postaxial polydactyly with an extra digit adjacent to the fifth digit, so a bony abnormality with a sharp kyphosis and open spinal defect and other anomalies.

Scoliosis

Scoliosis in distinction to kyphosis refers to abnormal lateral spinal curvature. This could be right or left sided or actually an S-shaped wave in both directions involving different spinal segments. In the fetal cases, scoliosis is usually caused by again, a vertebral anomaly, and this can be absent bones, fused bones or hemivertebrae. Neural tube defect is known to be associated in scoliosis in about 60% of the cases, and it can also be seen in other anomalies such as limb body wall complex, amniotic band syndrome, VACTERL association, and so forth.

This is an example of a fetus with severe scoliosis. You can see the marked curvature in the spine that again begins at about T nine or so and extends downward. These 2D images show you the abnormal curvature of the spine, and here we can see that the conus medullaris actually ends at a normal level. At about L two, this was a case that was referred for an abdominal wall defect and the scoliosis was completely missed.

We can see that in this setting of oligohydramnios, there's marked curvature laterally of the spine. Beginning from the region of the cervical spine, there's associated ventriculomegaly. And on this clip there is a large abdominal wall defect. We can see that there are herniated bowel loops outside of the abdominal cavity. This is the cardiac activity in the region of the heart. Here's the region of the chest and the lungs. So marked spinal curvature, scoliosis in a limb body wall complex case.

Spina Bifida

Now let's move on to spina bifida, where we are gonna spend most of our time because this is the most common central nervous system anomaly that's compatible with life. The open spinal defect is the least severe of the neural tube defects. Since anencephaly and encephalocele are much more difficult to manage and often not compatible with life in the US.

The incidence of spina bifida has remained relatively stable at about 1 in 500 cases a year, or 3.4 per 10,000 live births. The vast majority of these cases are associated with Chiari II type malformations, with hindbrain herniation, and abnormal brainstem and a very small and crowded posterior fossa. Live born infants often have hydrocephalus and other brain abnormalities with an estimated death rate of approximately 10%.

The recognized causes of neural tube defects are so wide and variable. They can be grouped into categories including maternal factors such as diabetes and a positive family history, as well as teratogens such as valproic acid, hypervitaminosis A. Neural tube defects may also be associated with chromosomal abnormalities, including trisomy 13, 18 and triploidy.

The pathogenesis of neural tube defects is not completely understood, and there are two theories, one related to failure of rostral and caudal closure, and then another that theorizes that the neural tube actually closes. There is some insult. And then the tube reopens after its formation.

A lot of what we have learned about spina bifida and myelomeningocele, if you will, has been related to the correlation between the sheep and human models. Here's an example of a sheep that was evaluated with an artificially created spinal defect in a laboratory and here after birth we can see that this sheep has paralysis of the lower extremities similar to this human case of again, a lumbosacral myelomeningocele and paralysis of the lower extremities after birth.

The prenatal natural history of myelomeningocele is believed to be after exposure of the neural elements to the non-sterile amniotic fluid, there is damage to the spinal cord and the peripheral nerves. And this damage results in hindbrain herniation with associated central nervous system findings with tethering of the cord and the open defect with exposure of the neural elements to the amniotic fluid ultimately causing paralysis, bowel and bladder abnormalities, orthopedic deformities and so forth with the severity of the lower limb deficits directly related to the level of the spinal injury.

Here's another graphic example of again, a L five to S one myelomeningocele in a fetus with trauma continuing throughout the pregnancy until this is the appearance of the defect after birth, you can notice how the lesion appears after additional weeks of exposure to the amniotic fluid. And here is a view of the newborn with the lower extremity abnormalities resulting from this further damage related to the toxic effects of the amniotic fluid.

The MOMS Trial

Recently, the MOMS trial, which was entitled Management of Myelomeningocele Study, was reported in the literature. This was an NIH funded trial at three centers, Children's Hospital of Philadelphia, University of California at San Francisco and Vanderbilt, where over a thousand women were screened for seven years. 183 women were ultimately randomized to pre or postnatal therapy, and the trial was recently stopped earlier this year due to proof of efficacy. The results were reported in the New England Journal of Medicine in February, 2011, and the results are very interesting.

First off, the inclusion criteria were that these women had to be residents of the United States. They had to have a singleton pregnancy in the first trimester, 19 less than 26 weeks. They had to have a myelomeningocele from T one to S one maternal age greater than 18 weeks, a normal karyotype and evidence on ultrasound of hindbrain herniation.

The exclusion criteria were if there were other anomalies, there were risks of preterm birth, including abruption or if the patients were morbidly obese with a high BMI. And finally, if there were surgical indications contraindications due to prior cesarean sections or surgery on the uterus itself.

Here's an example of images showing exactly how the surgical procedure is performed. Here we can see the hysterotomy has been done. The lesion is exposed. You can see the myelomeningocele defect there. The sac has been opened and we can see the opening in the spine. These images are showing the defect with the closure and here is what the fetus looks like after delivery with the postnatal closure site that you can see there.

The reason the trial was stopped is that as the preliminary results were being analyzed, it became clear that the outcome for prenatal therapy was better than postnatal therapy. And the newborns were followed at 12 and 30 months and the fetuses that underwent prenatal treatment, 36% had no hindbrain herniation at birth compared to only 4% of the postnatal group. 32% had improved lower extremity function, two levels of greater compared to 12% of the postnatal group. 42% could walk independently compared to 21% of the postnatal group and 40% required ventricular peritoneal shunt placement compared to 82% of the postnatally randomized group.

Here's an example of the human fetal MMC repair, and this is a diagram showing the herniated spinal contents and after surgery how the contents are returned to the spinal canal and the repair is done. And the theory is that there is reversal of the hindbrain herniation with the cerebellar tonsils returning to a more normal position in the posterior fossa after release of the neural placode and repair of the open spinal defect.

This is just an article from the Philadelphia Inquirer, published in February of this year. And this is an 11-year-old who was one of our first fetal repair cases at the Children's Hospital of Philadelphia. And this young lady can do aerobics and she takes dance and her only limitations are that she has to wear her braces several times per week.

Ultrasound Assessment of Spina Bifida

So let's look at what ultrasound the role that ultrasound played in analysis of these patients. What do we do for the spinal assessment? First off, we had to determine the level of the defect We needed to visualize the conus medullaris measure the sac and the skin defect, characterize its contents, was the sac purely cystic or did it contain neural elements? Evaluate for other neural axis anomalies and evaluate the lower extremities from movement from the hips to the toes.

On this slide, this is an example of how we determine the level of the defect. This is a myelomeningocele case using a 12 megahertz transducer, we can see ribs 10, 11, and 12 and then count the ossification centers for the lumbar spine. So we can see that this defect starts exactly at L two, counting down and extends all the way to the end of the sacrum at approximately S four.

This is a view showing the conus medullaris ending at the level of the defect with the cord tethered to the site of the abnormality. On this axial transverse view, we can see the wide splaying of the posterior arches and the thin little membrane covering the defect.

This is a cine clip showing another case where we can see that we measure the size of the myelomeningocele sac in three dimensions, AP and length on the sagittal view, and width on the transverse view. This shows the neural elements extending into the sac and they appear as solid, usually linear structures in this area of cystic sac with CSF fluid.

This is an example of what we do for the lower extremity evaluation. This is a fetus that is actually playing with the paralyzed lower extremities. These are the hands touching the feet compared to this normal case where there's flexion and extension at the hip, the knee and the ankle joint In this fetus who's being stimulated, one clue to a possible lower extremity abnormality is if the lower extremities remain crossed throughout the examination for more than an hour or so. That's generally a tip off that we are not getting normal spontaneous movement and there may be talipes.

Here's an example of a more severe case of talipes showing the muscular atrophy and thinning of the soft tissues involving the lower leg. Here we can see the foreleg. This is the area of the ankle on this 3D view and we can see the toes pointing towards the foot, a very abnormal appearance in a fetus that was difficult to evaluate due to the breech presentation. We can see the spinal defect here in the lower lumbosacral spine region and this is actually a transvaginal scan showing the measurement of the skin defect that measured over two centimeters.

Classification of Spina Bifida

It is possible to classify spina bifida a number of different ways. Spina bifida occulta generally refers to a subtle abnormality that we often can see on x-rays. Sometimes these are not detected until adult life and in some newborns these can present as a sacral dimple or hair tuft. Generally these patients will have a normal cord and nerves spina bifida.

Cystica on the other hand, refers to the open defects which contain either CSF fluid only without neural elements in the rare meningocele or more commonly neural elements and cerebral spinal fluid in the typical myelomeningocele.

Occult Spinal Defects

Now let's look at the occult spinal cases first. There are various types of occult defects ranging from the tethered cord to lipoma cyst, a split cord or a myelocystocele, and we'll look at some examples.

The tethered cord typically refers to the fact that the spinal cord is attached to the surrounding tissues of the back. This most often occurs as you've seen in examples shown before now in the open neural tube defect cases, but it can also be seen in lipomas, sacrococcygeal teratomas and other types of structural abnormalities.

Again, here's an example of a tethered cord with the conus medullaris and its flame shape or arrow shape ending at L five. And here's another example with again, the conus medullaris is flame shape ending at approximately L three to four, which is lower than expected.

This is an example of a tethered cord. This patient was referred in for a possible open neural tube defect and we can see that there's thickening of the skin and a calcified echogenic focus in the soft tissues of the subcutaneous area of this fetus. We can see that the cord is tethered and ends at about L four, but that this is not an open neural tube defect and it was easily repaired after birth and the cord was released with a good outcome.

Diastematomyelia refers to a quote unquote split cord or a division of the spinal cord into two hemicords. These usually have two dural sacs and it can occur because of a bony spur, A cartilaginous septum or even a band clefting can involve the cord, the conus medullaris or the filum terminale. This most often occurs in open neural tube defects and is much easier to visualize with MR than with ultrasound.

Here's an example of a split cord, if you will, with two sacs. Here's fluid here and here's fluid there. And you can see the split. This is the cord coming down, going to one sac and here's the other portion of the cord coming down and we can see a view of the two split sacs on this scan. And interestingly in this case, there was no evidence of ventriculomegaly or Arnold Chiari type malformation or hindbrain herniation, if you will.

Here's another example with again, a split cord where we can see the fibers of the spinal cord coming down and splitting into two in the lumbosacral area, again, a coronal view showing the fluid separating the spine there into two specific hemicords in this case of an open neural tube defect or myelomeningocele.

This is an interesting case of a high thoracic lesion. This is in the thoracolumbar spine. We can see that there is a bony spur in the middle of the cord here that we can see on the clip. This is a view showing the cord split around the bony spur and here is that the level of the defect. We can see that there's also an open spinal defect with the skin covering with a thin membrane here. And this is a view showing the wide splaying of the posterior arches and the bony bridge here. Wide splaying of the posterior arches, a thin little membrane. So this was a thoracolumbar myelomeningocele associated with diastematomyelia.

Finally for terminal myelocystocele, this is a very rare occult spinal defect that occurs typically in the lumbosacral region. It can be isolated or associated with the OEIS complex. Generally there's a large impendent terminal cyst often with overlying skin and thickening and the cord is usually tethered to the site of the defect. These types of lesions cannot be detected with maternal serum and amniocentesis testing as the AFP and the AChE are often normal.

Why is differentiation with the myelomeningocele important? The prognosis in these cases is usually excellent with good intellectual and neuromuscular function. It is a sporadic defect and so there is not a high recurrence risk with other open spinal defects. Counseling is also important to determine if the patients were on any medications or possible teratogens which can be associated with a terminal myelocystocele.

Here was a case of a myelocystocele that was surgically repaired at Children's Hospital. We can see that there is a cystic mass, very thick wall with an echogenic appearing component and notice that there is no hindbrain herniation. The cerebellum has a normal configuration and there's fluid in the region of the cisterna magna. This case was originally referred in as an echogenic mass, possibly a sacrococcygeal teratoma, but in fact it was proven to represent a terminal myelocystocele and there was lipomatous tissue associated with this.

Cystica: Meningocele vs. Myelomeningocele

Now let's move on to the other classification of spina bifida. Rather than just the occult versus the obvious lesion, spina bifida can be classified as cystica and in the cystica cases it can be either meningocele or myelomeningocele.

In meningocele, the contents of the sac is generally fluid and meninges and so it appears very cystic in appearance. The spinal cord and the nerve roots are typically normal. In the myelocystocele there's more of a solid component because neural elements are present and these cases are virtually always associated with tethered cord. And on Chiari II malformation or hindbrain herniation, here's an example of a meningocele where the sac is evident on these images and notice that there is fluid with no solid components visualized. There is rounding of the cerebellum, but a very thin area of about two millimeters of narrowing with residual fluid. A very small amount left in the region of the cisterna magna, which was not totally effaced. Also noticed that you can see fluid in the regions of the subarachnoid space, which was not completely crowded and effaced as well.

This is a much more typical myelomeningocele. And on this clip we can see the solid elements extending into the large myelomeningocele sac. Again, the anechoic areas represents cerebral spinal fluid and the more solid elements represent the neural tissues with the cord tethered to the site of the defect, which we can see here on this static image.

These are two axial images showing that the bony defect is generally about a level or two above the level of the skin defect. Here are the two posterior neural arches and they are gradually opposed, but at this level the skin and muscle appears to be closed. And then one level down, we can see we are at the level of the soft tissue defect where there is a frank opening with exposure of the tissues to the amniotic fluid.

Closed vs. Open Defects

Spina bifida can be classified as these are closed in approximately 20%, which means these cases are skin covered or have a thick opaque membrane. Again, these are usually detected only by imaging and not with a screening of serum. And then the open defects, which are much more common, 80% that are either uncovered or covered by a very thin translucent membrane. In these cases, there is direct communication again of the spinal contents with the amniotic fluid and these can be readily detected on maternal serum screening and on amniocentesis, here's an example of a closed spinal defect that is actually skin covered and we can see as we go down from S one to S two that there is a thick covering of the skin. Here we can see the abnormal appearance of the cord, which goes into the area of the small defect, but again, the covering of the skin is protective and so this type of defect could not be discovered just on routine maternal serum screening.

This is an example of a more typical open spinal defect from L two to S four. We use the term myelschisis to refer to this type of opening in which the defect is very flat. There is no measurable sac. There is basically just a hole where the spinal tissues did not converge normally. And if you notice these actual views here at L one, the posterior arches are closely opposed. They start to gradually separate at L two with a subtle bony defect, a little bit more separated at L three and then more widely splayed at L four at the level of the skin defect.

Open spinal defects, the vast majority tend to occur in the lumbar region, 73%, 17% in the sacrum, 9% in the thorax, and 1% in the cervical region. Here's an example of a thoracic myelomeningocele, and we can see on this cine clip that there is a sac in the thoracic region with reconstitution of the soft tissues and the skin in the region of the lower lumbar and sacral spine. We can see the degree of hindbrain herniation with a rounded cerebellum that completely effaces the cisterna magna. And we can also see the degree of ventriculomegaly with the dangling choroid plexus on this clip. And here is the degree of ventriculomegaly. Notice that the lower extremities still display very normal spontaneous motion without evidence of talipes.

Cervical myelomeningoceles are very rare and here's an example of such a case showing that there is a defect in the upper spine in the region of the cervix. We can see this large defect measured here. And in addition, there is a cystic malformation involving the cord itself and here we can see the spinal cord. So this was a cervical cord syrinx associated with a rare cervical myelomeningocele.

This is the same patient showing a more axial view with a defect extending from C seven to T one. And here on this view we can see the covering and the large defect. And at this region we can see the cystic area of the syrinx. Notice that there is complete hindbrain herniation with the cerebellar tonsils extending into the cervical spine region. There is severe cerebral ventricular enlargement measuring 2.8 to 2.5 centimeters with a dangling choroid plexus. And here is a region of the conus medullaris. Interestingly, that ended at L two to three in the normal level.

Associated Cranial Findings

There are known to be cranial findings associated with open spinal defects and these range from ventriculomegaly to the fruit signs, lemon and banana, cisterna magna effacement or an Chiari II malformation if you will. Another term is hindbrain herniation, and if that is severe, there can also be associated microcephaly.

This is an example to illustrate the importance of trying to visualize both lateral cerebral ventricles. The non-dependent ventricle often can be filled with electronic noise, but here we can see that the left ventricle, which was non-dependent, measured 13 millimeters compared to the dependent right ventricle, which was only 10 millimeters.

This is another case of myeloschisis. We can see that there is a flattened defect without a well-defined sac on this axial view, splaying of the posterior arches with a thin covering membrane. This is an example of the lemon sign which refers to concave frontal bones. And here we can see the lemon appearance of the frontal bones. Interesting in this case in that there was no ventriculomegaly, the ventricles both measured less than eight millimeters. The spinal cord was tethered to the site of the defect that we see here. And again, here we can see that this was a low sacral lesion without ventriculomegaly, but with a nice lemon sign.

So what is the value of the signs in the brain? Normal cerebral ventricles and the spine On an outside scan? If you see the fruit signs, it means that we must go back and do a much more detailed evaluation to try to pick up a very subtle abnormality. Here is a case showing the ventricles that are measuring five millimeters. There is frontal bone concavity with the lemon sign and the abnormal curvature of the cerebellum with the banana sign. In a case such as this, we would need to go and do an extremely detailed evaluation of the spine all the way to the very lower spine to make sure that any potential lesion was discovered.

And here is a case of where the S four lesion is so low and so subtle that what led to a second opinion searching for the abnormality was the persistence of the CNS findings. And here on this clip, if you follow it down, you can see how the spine looks formed. Normally the posterior arches are relatively well opposed. However, when we get to the very, very lower area of the sacrum, we can see the divot in the soft tissues and a tiny little cystic abnormality here that is indicated here by this arrow here is a subtle splaying of the posterior arches there and here is a view using a 12 megahertz transducer showing the conus medullaris tethered to the site of the defect, a very low sacral lesion with subtle CNS findings, which tipped us off to search diligently for the correct diagnosis which was missed on the outside scan.

What are the accuracies of these markers in the brain? The lemon sign is extremely sensitive, as is the abnormal cerebellum or banana sign. However, the posterior fossa is more valuable because the abnormal cerebellum tends to remain throughout the gestation, whereas a lemon sign may resolve as the skull and cranial tissues mature and therefore it has been reported that in the later third trimester, later second and third trimester, that a lot of cases will not necessarily have the lemon sign but will have the banana sign due to the abnormal crowding of the posterior fossa and the hindbrain herniation associated with myelomeningocele.

This is an example of pseudomicrocephaly in a case with severe hindbrain herniation. And here we can see that the ventricles, again, were just at the number of 10. The chart shows the BPD was two standard deviations below the mean due to the severe degree of hindbrain herniation. This is a coronal view showing the cerebellar tonsils downward. This is a view showing the inability to oppose the two posterior arches with this subtle variation due to a little scoliosis at the area of the defect. And you can see the curvature. This is a cord tethered to the site of the defect, but due to the degree of hindbrain herniation, the head measurements did not fall within the expected normal range.

Prognostic Factors

Let's move on to the prognostic factors associated with spinal defects, specifically open spinal defects. There can be other associated anomalies involving other organ systems, and it is important to note this for the counseling of the parents. It is also important to determine, as we have previously discussed, the location and the size of the defect. Characterize it as open and closed or closed and evaluate the degree of ventriculomegaly or hydrocephalus for pregnancy management.

This is an example, another case of thoracolumbar scoliosis associated with an open spinal defect. Here we can see the thin covering membrane, the abnormal cerebellum with the banana shape. And notice that again, the ventricles measured within the range of normal at nine and 10 millimeters and the choroid plexus actually touches the lateral and medial ventricular wall. But there were other associated anomalies. Here is a clip again showing that thoracolumbar scoliosis notice that there's a grossly abnormal left hand with persistent flexion at the wrist and there is severe bilateral talipes with the legs crossed at the ankles with no spontaneous motion and atrophy of the muscles of the lower leg.

This is another example of a myelomeningocele with a number of associated abnormalities. Here we can see the large myelomeningocele sac both on the longitudinal and the axial view measured in all three planes. The associated hindbrain herniation with the abnormal appearing cerebellum. The ventricles again just at the magic number of 10, but here we can see the herniated tonsils and the step off of the cervical vertebrae. There was an associated widening of the cervical canal due to a syrinx of the cervical cord.

Sacral Coccygeal Teratoma

Let's end up now with sacral coccygeal teratoma, which is a rare tumor that arises from the cells of the coccyx. It can occur in association with neural tube defects or other spinal abnormalities. Histologically. There are four different types, one to four and most masses tend to be solid or complex. A tip off is if you see focal calcifications and those mixed in with cystic components as well as vascular flow on color Doppler can help make the diagnosis.

There are complications with these tumors, particularly cardiovascular compromise resulting in non-immune hydrops due to vascular steal from the solid components of these lesions. Here is a table showing the SCT classification. The type one lesions are predominantly external with only a small presacral component. Type two lesions have a little bit more external component, but type three tends to be predominantly internal and the rare type four is entirely internal.

So let's look at some examples. Here's a large, predominantly solid and hypervascular type one lesion. This color doppler shows flow from the iliac arteries feeding this very large complex lesion that has a few scattered cystic components, but is solid for the most part. The vascular steal in this case resulted in cardiac compromise with a dilated inferior vena cava. And these are 3D renderings here showing the large mass with the appearance that looks like the fetus sitting on a basketball.

What are prognostic factors that influence the outcome in SCT patients? Large, solid hypervascular lesions put the fetuses at greatest risk. Children's Hospital reviewed their SCT patients a few years ago and looked at about 30 fetuses that we examined over an eight year period and noticed that the complications developed in about 80% of the cases. Polyhydramnios, there can be too much fluid. Oligohydramnios is too little fluid. Preterm labor was a problem as well as preeclampsia and so forth as you see listed here. Of the 30 cases we actually did in utero surgery on three and three survived after intervention. There were six cases that were predominantly cystic and were treated with cyst aspiration, amnio reduction or amnio infusion.

Here's an example of a patient that's at significant risk of developing non-immune hydrops due to a large type one, predominantly solid sacrococcygeal teratoma. And here on these 3D images, we can see the lesion in the region of the buttocks here and here for our sonographic assessment of these tumors.

What we do is we evaluate the placenta to assess for possible placentomegaly. We look at the amniotic fluid for either too much or too little fluid and measure both the amniotic fluid index and the deepest vertical pocket. We search for additional signs of non-immune hydrops. We classify the SCT as to types one to four. We measure the volume of the mass using the formula for a prolate ellipse and that is width times length, times height, times 0.523. We look at the texture of the lesion and try to characterize that as predominantly complex, solid or cystic. We assess the vascularity with color doppler and we evaluate the umbilical artery including the umbilical vein and the ductus venosus again for tip offs of any compromise.

Here's an example of a very extensive type three sacrococcygeal teratoma. Here we can see that there's wide splaying of the bones of the lower pelvis. Here this mass extends internally and we can see that there's associated ascites fluid here. The mass effect pushes the liver up and notice on power doppler. There's extensive vascular flow to this patient who presented with non-immune hydrops and severe oligohydramnios. This is the corresponding MRI that shows this huge lesion and the lack of amniotic fluid in this case with oligohydramnios.

What other complications can be associated with SCT besides non-immune hydrops? And that includes a thickening of the placenta, again, oligohydramnios or polyhydramnios without frank non-immune hydrops. We look for signs of cardiovascular compromise. The mother can actually start to mirror the fetal symptoms and actually get maternal mirror syndrome with swelling of the ankles and cardiovascular compromise. And there can be specific complications associated with the mass effect of the tumor or the overall tumor volume.

Here's another case of a solid hypervascular type one sacrococcygeal teratoma that is predominantly external and again with significant vascular steal on power doppler. Here we can see the aorta and the vessel supplying This mass here we can see is predominantly solid. Notice the distended inferior vena cava and the finding of polyhydramnios with fluid pockets greater than nine centimeters.

Anomalies that can be associated with SCT volume specifically involve the genitourinary tract. The gastrointestinal tract, pulmonary hypoplasia can develop musculoskeletal abnormalities such as clubfoot and hip dislocation and central nervous system complications including invasion of the spinal cord by the enlarging mass.

This is an example of a large solid type two SCT. We can see that there is a very large external component but also an element of an internal component bigger than in the type one sort of lesions. Color doppler shows the vascular flow to this lesion, and if you look on this view, there is a solid sheath of tissue extending into the area of the spinal canal due to spinal cord involvement. We can prove this by turning on color doppler and you can see that there's a large blood vessel extending into the region of the spinal cord. And spectral analysis of that vessel shows that there's clear vascular flow extending into the region of the spinal canal with intrathecal flow, definitively diagnosing spinal cord invasion by this large SCT.

This is a CT that an SCT that has much more internal component. This is a type three and we can see that vessels are displaced. The mass extends high into the abdomen out of the true pelvis. This is the obstructed uterus and we can see that it is filled with debris. There is ascites fluid and here is a large mass pressing on the region of the cervix in the lower uterine segment of obstructing the uterus due specifically to volume.

These are additional images on that same patient showing bilateral hydronephrosis with thinning of the cortex and ballooning of the calyces. We can see here that the mass presses on the bladder, which is distended and extends up to the level of the gallbladder. Here again, we see the volume of this large mass, which measures five by six centimeters on some views. Another view showing the extension of the mass with a complex cystic and solid components extending up to the level of the liver and the gallbladder. And here on this view vascular flow in the region of the sacrum indicating intrathecal growth into the region of the spinal canal due to invasion by this very large sacrococcygeal teratoma.

This is a rare type four lesion with massive abdominal distension due to the fact that the tumor is entirely internal in location. And this view shows that this is not ascites fluid with floating bowel, but this is the entire mass with both a cystic and solid component. And here you can see the solid components with a large more peripheral cystic component. You can see that the diaphragm is elevated, the lungs are compressed with this huge type four SCT lesion.

There's no therapy that can be done really for the type three and type four lesions due to the mass volume of these lesions. And the internal location type one lesions can be treated various ways. Here is a type one lesion that is predominantly cystic. On this power doppler image, you can see that fluid goes from one locule into the next locule. And this patient with thick nodular septations was managed by having a fluid drained from these various cystic components as the mass enlarged and in preparation for delivery in order that there would be less of a mass effect to have to deal with at the time of delivery due to decompression of these cystic spaces by aspiration with multiple attempts.

Here's another patient that was aspirated serial times as the pregnancy was managed here we can see on this clip that there is a cystic mass extending off laterally. And here's another view showing the cystic mass that had minimal solid components and was managed with serial aspirations prior to delivery.

Conclusion

In conclusion, I believe that sonography of the spine is a very important area in fetal anomaly diagnosis. We can make many specific diagnoses now using the high frequency probes that are available with the latest equipment, and here is one of our fetuses that is smiling because he was able to survive after appropriate counseling and management of his spinal defect. Thank you for your attention.