The Rationale for in utero repair of myelomeningocele

Implication of chromosomal microarray analysis prior to in-utero repair of fetal open neural tube defect

OBJECTIVE

In-utero repair of open neural tube defects (ONTD) is an accepted treatment option with demonstrated superior outcome for eligible patients. While current guidelines recommend genetic testing by chromosomal microarray analysis (CMA) when a major congenital anomaly is detected prenatally, the requirement for an in-utero repair, based on the Management of Myelomeningocele Study (MOMS) criteria, is a normal karyotype. In this study, we aimed to evaluate if CMA should be recommended as a prerequisite for in-utero ONTD repair.

METHODS

This was a retrospective cohort study of pregnancies complicated by ONTD that underwent laparotomy-assisted fetoscopic repair or open-hysterotomy fetal surgery at a single tertiary center between September 2011 and July 2021. All patients met the MOMS eligibility criteria and had a normal karyotype. In a subset of the pregnancies (n = 77), CMA testing was also conducted. We reviewed the CMA results and divided the cohort into two groups according to whether clinically reportable copy-number variants (CNV) were detected (reportable-CNV group) or not (normal-CMA group). Surgical characteristics, complications, and maternal and early neonatal outcomes were compared between the two groups. The primary outcomes were fetal or neonatal death, hydrocephalus, motor function at 12 months of age and walking status at 30 months of age. Standard parametric and non-parametric statistical tests were employed as appropriate.

RESULTS

During the study period, 146 fetuses with ONTD were eligible for and underwent in-utero repair. CMA results were available for 77 (52.7%) patients. Of those, 65 (84%) had a normal CMA and 12 (16%) had a reportable CNV, two of which were classified as pathogenic. The first case with a pathogenic CNV was diagnosed with a 749-kb central 22q11.21 deletion spanning low-copy-repeat regions B-D of chromosome 22; the second case was diagnosed with a 1.3-Mb interstitial deletion at 1q21.1q21.2. Maternal demographics, clinical characteristics, operative data and postoperative complications were similar between those with normal CMA results and those with reportable CNVs. There were no significant differences in gestational age at delivery or any obstetric and early neonatal outcome between the study groups. Motor function at birth and at 12 months of age, and walking status at 30 months of age, were similar between the two groups.

CONCLUSIONS

Standard diagnostic testing with CMA should be offered when an ONTD is detected prenatally, as this approach has implications for counseling regarding prognosis and recurrence risk. Our results indicate that the presence of a clinically reportable CNV should not a priori affect eligibility for in-utero repair, as overall pregnancy outcome is similar in these cases to that of cases with normal CMA. Nevertheless, significant CMA results will require a case-by-case multidisciplinary discussion to evaluate eligibility. To generalize the conclusion of this single-center series, a larger, multicenter long-term study should be considered. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Long-term neurological cognitive, behavioral, functional, and quality of life outcomes after fetal myelomeningocele closure: a systematic review

BACKGROUND

Myelomeningocele is a lifelong condition that features several comorbidities, such as hydrocephalus, scoliosis, club foot, and lower limb sensory and motor disabilities. Its management has progressed over time, ranging from supportive care to early postnatal closure to prenatal closure of the defect. Recent research discovered that fetal myelomeningocele closure (fMMC) provided superior neurological outcomes to those of postnatal closure. When performed at 12 months of age, fMMC can avert or delay the need for a ventriculoperitoneal shunt and reversed the hindbrain herniation. Moreover, fMMC reportedly enhanced motor function and mental development at 30 months of age. However, its long-term outcomes remain dubious.

PURPOSE

This systematic review aimed to determine the long-term neurological cognitive, behavioral, functional, and quality of life (QoL) outcomes after fMMC.

METHODS

The PubMed, Directory of Open Access Journals, EBSCO, and Cochrane databases were extensively searched for articles published in 2007-2022. Meta-analyses, clinical trials, and randomized controlled trials with at least 5 years of follow-up were given priority.

RESULTS

A total of 11 studies were included. Most studies revealed enhanced long-term cognitive, behavioral, functional, and QoL outcomes after fMMC.

CONCLUSION

Our results suggest that fMMC substantially enhanced patients' long-term neurological cognitive, behavioral, functional, and QoL outcomes.

Neurosurgical procedures for children with myelomeningocele after fetal or postnatal surgery: a comparative effectiveness study

AIM

To compare the frequencies of neurosurgical procedures to treat comorbid conditions of myelomeningocele in patients who underwent fetal surgery versus postnatal surgery for closure of the placode.

METHOD

By utilizing the National Spina Bifida Patient Registry in a comparative effectiveness study, 298 fetal surgery patients were matched by birthdate (±3mo) and spina bifida clinic site with one to three postnatal surgery patients (n=648). Histories were obtained by record review on enrollment and yearly subsequently. Multivariable Poisson regression was used to compare frequencies of procedures between cohorts, with adjustments for sex, ethnicity, insurance status, spinal segmental level of motor function, age at last visit recorded in the Registry, and, for shunt revision in shunted patients, age at cerebrospinal fluid (CSF) diversion.

RESULTS

The median age at last visit was 4 years. In fully adjusted analyses in patients aged at least 12 months old, fetal surgery was associated with decreased frequency of CSF diversion for hydrocephalus by ventriculoperitoneal shunt insertion or endoscopic third ventriculostomy compared with postnatal surgery (46% vs 79%; incidence rate ratio=0.61; 95% confidence interval [CI] 0.53-0.71; p<0.01). Over all ages, fetal surgery was associated with decreased frequency of Chiari decompression for brainstem dysfunction (3% vs 7%; incidence rate ratio=0.41; 95% CI 0.19-0.88; p=0.02). Also over all ages, differences were not significant in frequencies of shunt revision in shunted patients (53% vs 55%; incidence rate ratio=0.87; 95% CI 0.69-1.11; p=0.27), nor tethered cord release for acquired spinal cord dysfunction (18% vs 16%; incidence rate ratio=1.11; 95% CI 0.84-1.47; p=0.46).

INTERPRETATION

Even with the variations inherent in clinical practice, fetal surgery was associated with lower frequencies of CSF diversion and of Chiari decompression, independent of covariates. What this paper adds Fetal surgery was associated with lower frequencies of cerebrospinal fluid diversion and decompression of Chiari II malformation than postnatal surgery. Frequencies of ventriculoperitoneal shunt revision and tethered cord release were not significantly different between cohorts.

[Prenatal ultrasound prognostic of myelomeningocele at the era of fetal surgery]

Myelomeningocele (MMC) is a severe congenital condition responsible for motor and sensory impairments of the lower limbs, incontinence and cognitive impairment. Its screening, sometimes as early as the first trimester, is one of the major goals of modern prenatal care, supported by the emergence of prenatal surgery that results in a significant improvement in motor function, ambulation and ventriculoperitoneal shunt rate in patients undergoing in-utero surgery. From screening to pre- and post-operative prognostic evaluation, prenatal ultrasound is now an essential tool in the antenatal management of this condition. Using the multi planar and three-dimensional modes, it can be used to assess the vertebral level of MMC, which remains the key antenatal prognostic marker for motor function and ambulation, incontinence and the need for a ventriculo-peritoneal shunt. A careful and systematic ultrasound examination also makes it possible to assess the severity and progression of ventriculomegaly, to search for associated cerebral, spinal cord or vertebral anomalies, or to rule out exclusion criteria for in-utero surgery such as severe kyphosis or serious cortical anomalies. New tools from post-natal evaluation, such as the "metameric" ultrasound assessment of lower limb mobility, appear to be promising either for the initial examination or after in-utero surgery. Ultrasonography, associated with fetal MRI, cytogenetic and next generation sequencing, now allows a highly customized prognostic evaluation of these fetuses affected by MMC and provides the parents with the best possible information on the expected benefits and limitations of fetal surgery.

Accuracy of qualitative and quantitative cranial ultrasonographic markers in first-trimester screening for open spina bifida and other posterior brain defects: a systematic review and meta-analysis

BACKGROUND

The significant number of qualitative and quantitative ultrasound markers described for first-trimester screening of open spina bifida (OSB) and other posterior brain defects (oPBD) has resulted in their complex implementation and interpretation for a widespread screening and in a lack of consensus regarding diagnostic accuracy.

OBJECTIVES

To assess and compare the accuracy of qualitative and quantitative cranial sonographic markers at 11-14 weeks of gestation for the detection of OSB and oPBD.

SEARCH STRATEGY

A systematic literature search was performed in MEDLINE and COCHRANE from 2009 to April 2020.

SELECTION CRITERIA

Studies assessing the diagnostic accuracy of quantitative and/or qualitative ultrasound signs to predict OSB and oPBD were included. Cohort studies and case-control studies were also considered.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed the risk of bias. The overall pooled estimate and a summary receiver operating characteristic curve was estimated for each subgroup (qualitative and quantitative assessment).

MAIN RESULTS

Twenty-three studies were included in our meta-analysis. The pooled sensitivity and specificity for qualitative assessment were 76.5% and 99.6%, and for quantitative assessment were 84.5% and 96.3%, respectively; specificity for the qualitative ultrasound signs was significantly higher (P = 0.001). The overall sensitivity of cranial sonographic markers for the screening of oPBD was 76.7% and specificity was 97.5%.

CONCLUSIONS

The qualitative approach demonstrated greater specificity, so this would appear to be more appropriate for daily screening, as a first-line tool, whereas the quantitative approach should be reserved for expert ultrasound.

TWEETABLE ABSTRACT

This study highlights the relevance of first-trimester qualitative ultrasound signs in the screening of open spina bifida.

Nervous System Malformations

PURPOSE OF REVIEW

This article provides an overview of the most common nervous system malformations and serves as a reference for the latest advances in diagnosis and treatment.

RECENT FINDINGS

Major advances have occurred in recognizing the genetic basis of nervous system malformations. Environmental causes of nervous system malformations, such as perinatal infections including Zika virus, are also reviewed. Treatment for nervous system malformations begins prior to birth with prevention. Folic acid supplementation reduces the risk of neural tube defects and is an important part of health maintenance for pregnant women. Fetal surgery is now available for prenatal repair of myelomeningocele and has been demonstrated to improve outcomes.

SUMMARY

Each type of nervous system malformation is relatively uncommon, but, collectively, they constitute a large population of neurologic patients. The diagnosis of nervous system malformations begins with radiographic characterization. Genetic studies, including chromosomal microarray, targeted gene sequencing, and next-generation sequencing, are increasingly important aspects of the assessment. A genetic diagnosis may identify an associated medical condition and is necessary for family planning. Treatment consists primarily of supportive therapies for developmental delays and epilepsy, but prenatal surgery for myelomeningocele offers a glimpse of future possibilities. Prognosis depends on multiple clinical factors, including the examination findings, imaging characteristics, and genetic results. Treatment is best conducted in a multidisciplinary setting with neurology, neurosurgery, developmental pediatrics, and genetics working together as a comprehensive team.

Outcomes of infants followed-up at least 12 months after fetal open and endoscopic surgery for meningomyelocele: a systematic review and meta-analysis

OBJECTIVE

To assess the outcomes of infants followed-up at least 12 months after open and endoscopic fetal surgery for the treatment of spina bifida.

METHODS

A searching in The Cochrane Library, LILACS, PubMed and SCOPUS databases for fetal meningomyelocele (MMC) open or endoscopic surgery in humans from 2003 on-wards with follow-up at least 12 months. The rate of the estimated proportions was evaluated by the 95% confidence interval (CI).

RESULTS

A total of 19 studies were finally included (17 open and 2 endoscopic surgery). The results suggested that the rate for ventriculoperitoneal shunt placement were 40% (29%, 51%) versus 45% (34%, 56%) for open surgery group and endoscopic surgery group. The rate of hindbrain herniation reversal was 34% (28%, 52%) versus 86% (49%, 97%), the lower extremity function rates for both groups were 47% (30%, 64%) versus 86% (49%, 97%), and bladder dysfunction rates for both groups were 72% (53%, 88%) versus 29% (8%, 64%), respectively. Open and endoscopic fetal surgery for MMC presented similar ventriculoperitoneal shunt rates.

CONCLUSION

Open and endoscopic fetal surgery for MMC presented similar ventriculoperitoneal shunt rates in infants followed at least 12 months.

Human amniotic fluid-derived mesenchymal cells from fetuses with a neural tube defect do not deposit collagen type i protein after TGF-β1 stimulation in vitro

In spina bifida, the neural tube fails to close during the embryonic period. Exposure of the neural tube to the amniotic fluid during pregnancy causes additional neural damage. Intrauterine tissue engineering using a biomaterial seeded with stem cells might prevent this additional damage. For this purpose, autologous cells from the amniotic fluid are an attractive source. To close the defect, it is important that these cells deposit an extracellular matrix. However, it is not known if amniotic fluid mesenchymal cells (AFMCs) from a fetus with a neural tube defect (NTD) share the same characteristics as AFMCs from a healthy fetus. We found that cells derived from fetuses with a NTD, in contrast to healthy human amniotic fluid cells, did not deposit collagen type I. Furthermore, the NTD cells showed, compared with both healthy amniotic fluid cells and fetal fibroblasts, much lower mRNA expression levels of genes that are involved in collagen biosynthesis [procollagen C-endopeptidase enhancer proteins (PCOLCE), PCOLCE2, ADAM metallopeptidase with thrombospondin type 1 motif, 2 (ADAMTS2), ADAMTS14]. This indicates that NTD-AFMCs have different characteristics compared with healthy AFMCs and might not be suitable for fetal therapy to close the defect in spina bifida patients.

Enhanced reclosure of surgically induced spinal open neural tube defects in chick embryos by injecting human bone marrow stem cells into the amniotic cavity

OBJECTIVE

To evaluate the reclosure-promoting capacity of a neural stem cell line (F3) and a human bone marrow stem cell line (B10) injected into the amniotic cavity of spinal open neural tube defects (ONTDs) of chick embryos of Hamburger and Hamilton stage 18 or 19.

METHODS

Fifteen chick embryos that survived the procedure were obtained for each of 4 groups: untreated control, F3-, B10-, and HFF-1 (human foreskin fibroblast)-treated groups. Embryos in the control group underwent ONTD surgery but no cell injection.

RESULTS

Compared with the untreated control and HFF-1 groups, the B10 group showed enhanced reclosure at 3, 5, and 7 days after injection, whereas the F3 group did not. B10 cells were not incorporated into reclosed neural tubes but simply covered ONTDs during the process of reclosure. F3 cells did not cover ONTDs. The cell survival of F3 cells exposed to the chick amniotic fluid in vitro for 48 hours was significantly lower than that of B10 cells.

CONCLUSION

The results confirmed that B10 cells enhance reclosure of ONTDs by covering and protecting neural tissues, not by direct cell incorporation. The lack of reclosure capacity in the F3 group may be related to the poor survival of F3 cells in the amniotic fluid.

Spinal cord malformations

Malformations of the spinal cord are one of the most frequent malformations. They should be clearly divided into two completely different families of malformations: open dysraphisms and occult dysraphisms. Open dysraphism mostly consists in myelomeningocele (MMC). Its incidence is 1/1000 live births with a wide variation. Folic acid supplementation has been shown to reduce its risk. In most cases, the diagnosis is done prenatally by serum screening and ultrasound and may lead to termination of pregnancy. In case of decision to continue pregnancy, surgical treatment must be achieved during the first days of life, and in 50 to 90% of cases, a ventricular shunt must be installed. The follow-up of these children must be continued throughout life looking for late complications (Chiari II and syringomyelia, vertebral problems, neuropathic bladder, tethered cord). Occult dysraphisms are a heterogeneous group of malformations. Lipomas (filum and conus) are the most frequent and their treatment remains controversial. Diastematomyelia, neurenteric cysts, dermal sinus, and more complex forms (Currarino syndrome) belong to this group. Most of them can and must be diagnosed prenatally or at birth by careful examination of the lower back for the cutaneous stigmata of the disease to decrease the risk of neurological, urological, or orthopedic permanent handicap.

Meconium staining of the brainstem with open myelomeningocele

Meconium staining of open myelomeningoceles has been reported to occur both prenatally and postnatally, but meconium staining of the brainstem has not been previously documented. The authors present a case of meconium staining of the brainstem in an infant with a meconium-stained myelomeningocele, Chiari malformation Type II, and hydrocephalus and discuss possible implications for prenatal and perinatal care.

Congenital stridor in the context of Chiari malformation type II: the etiological role of vernix caseosa granulomatous meningitis

The authors describe the case of a late preterm infant girl who presented prenatally with a low lumbar neural tube defect and features of Chiari malformation type II (CM-II). At birth, she exhibited stridor and underwent surgical repair of a lumbosacral myelomeningocele on Day 2 of life. The prognosis was deemed to be poor, and hence a "Chiari decompression" procedure was not undertaken. The patient was subsequently extubated and died on Day 10. Postmortem findings included a rarely described but characteristic granulomatous meningitic reaction to vernix caseosa, which presumably entered the subarachnoid space and spinal cord syrinx antenatally via the open neural tube defect. The significance of congenital stridor in the context of CM-II and in particular the role of vernix caseosa granulomatous meningitis are examined. The antenatal repair of myelomeningoceles, as championed by some, may prevent this ominous meningitic complication.

Congenital myelomeningocele - do we have to change our management?

BACKGROUND

Eagerly awaiting the results of the Management of Myelomeningocele Study (MOMS) and with an increasing interest in setting up intrauterine myelomeningocele repair (IUMR), the optimal management of patients suffering from congenital myelomeningocele (MMC) has become a matter of debate again. We performed a cross-sectional study at our referral-center for MMC to determine the outcome for our expectantly managed patients.

MATERIALS AND METHODS

A computed chart review at our institution revealed 70 patients suffering from MMC. Forty-three patients were eligible for the study and analyzed further. A retrospective analysis was performed only in patients that underwent MMC repair within the first two days of life and were seen at our outpatient clinic between 2008 and 2009 for a regular multidisciplinary follow-up. Data were collected on: gestational age (GA) and weight at birth, age at shunt placement and shunt status after the first year of life, radiological evidence for Arnold-Chiari malformation (ACM) and tethered cord (TC), need for surgery for TC, bladder function, lower leg function and educational level. Data were compared to published results for IUMR and to studies of historical controls.

RESULTS

Patients were born with MMC between 1979 and 2009 and are now 13.3 ± 8.9 (mean ± SD) years of age. At birth, mean GA was 37.8 ± 2.3 weeks and mean weight was 2921.3 ± 760.3 g, both significantly higher than in IUMR patients. Shunt placement in our cohort was required in 69.8% at a mean age of 16.0 ± 10.7 days, which was less frequent than for historical controls. Amongst our cohort, radiological observations showed 57.1% had ACM II and 41.9% had TC. Only two of our patients underwent a surgical correction for TC. Clean intermittent catheterization was performed in 69.7% of our patients, 56.4% were (assisted) walkers and 64.1% attended regular classes, both comparable to historical controls.

CONCLUSIONS

With a close and interdisciplinary management by pediatric surgeons, neurologists and urologists, the long-term outcome of patients suffering from MMC can currently be considered satisfactory. With respect to the known drawbacks of fetal interventions for mother and child, especially preterm delivery, the results of the MOMS trial should be awaited with caution before proceeding with a complex intervention like IUMR.

Anomalous development of brain structure and function in spina bifida myelomeningocele

Spina bifida myelomeningocele (SBM) is a specific type of neural tube defect whereby the open neural tube at the level of the spinal cord alters brain development during early stages of gestation. Some structural anomalies are virtually unique to individuals with SBM, including a complex pattern of cerebellar dysplasia known as the Chiari II malformation. Other structural anomalies are not necessarily unique to SBM, including altered development of the corpus callosum and posterior fossa. Within SBM, tremendous heterogeneity is reflected in the degree to which brain structures are atypical in qualitative appearance and quantitative measures of morphometry. Hallmark structural features of SBM include overall reductions in posterior fossa and cerebellum size and volume. Studies of the corpus callosum have shown complex patterns of agenesis or hypoplasia along its rostral-caudal axis, with rostrum and splenium regions particularly susceptible to agenesis. Studies of cortical regions have demonstrated complex patterns of thickening, thinning, and gyrification. Diffusion tensor imaging studies have reported compromised integrity of some specific white matter pathways. Given equally complex ocular motor, motor, and cognitive phenotypes consisting of relative strengths and weaknesses that seem to align with altered structural development, studies of SBM provide new insights to our current understanding of brain structure-function associations.

In utero meconium passage in fetuses and newborns with myelomeningocele

OBJECT

The authors retrospectively investigated whether midgestational fetal myelomeningocele (fMMC) repair alters intrauterine meconium exposure.

METHODS

Prior to the National Institutes of Health Management of Myelomeningocele Study, 54 fetuses underwent fMMC repair at the authors' institution. Forty-six fMMC sacs were available for pathological examination and 53 MMC sacs from postnatally repaired MMCs (pMMCs) were available for comparison. The presence and distribution of meconium were blindly evaluated using a grading system defined as follows: absent (no meconium present), mild (<10 meconium-positive histiocytes [MPHs]/hpf), moderate (10-25 MPHs/hpf), and severe (>25 MPHs/hpf). Hall's bile stain was used to confirm meconium and Prussian blue and Fontana Masson stains to exclude hemosiderin and melanin, respectively.

RESULTS

Compared to pMMCs (79%), meconium histiocytosis was less prevalent in fMMC sacs (57%; p=0.017). Meconium staining was completely absent in 43% of the fMMC sacs. Mild meconium histiocytosis was found in 35% fMMC and 61% pMMC sacs (p=0.035). There was no statistical difference between groups with moderate and severe meconium histiocytosis.

CONCLUSIONS

Meconium passage in MMCs can occur early in fetal life. Fetal MMC repair may reduce the duration of meconium exposure, thereby potentially limiting the toxic injury to the vulnerable neural elements.

Prenatal diagnosis and treatment planning of congenital heart defects-possibilities and limits

BACKGROUND

Newborns with hypoplastic left heart syndrome (HLHS) or right heart syndrome or other malformations with a single ventricle physiology and associated hypoplasia of the great arteries continue to be a challenge in terms of survival. The vast majority of these forms of congenital heart defects relate to abnormal morphogenesis during early intrauterine development and can be diagnosed accurately by fetal echocardiography. Early knowledge of these conditions not only permits a better understanding of the progression of these malformations but encourages some researchers to explore new minimally invasive therapeutic options with a view to early pre- and postnatal cardiac palliation.

DATA SOURCES

PubMed database was searched with terms of "congenital heart defects", "fetal echocardiography" and "neonatal cardiac surgery".

RESULTS

At present, early prenatal detection has been applied for monitoring pregnancy to avoid intrauterine cardiac decompensation. In principle, the majority of congenital heart defects can be diagnosed by prenatal echocardiography and the detection rate is 85%-95% at tertiary perinatal centers. The majority, particularly of complex congenital lesions, show a steadily progressive course including subsequent secondary phenomena such as arrhythmias or myocardial insufficiency. So prenatal treatment of an abnormal fetus is an area of perinatal medicine that is undergoing a very dynamic development. Early postnatal treatment is established for some time, and prenatal intervention or palliation is at its best experimental stage in individual cases.

CONCLUSION

The upcoming expansion of fetal cardiac intervention to ameliorate critically progressive fetal lesions intensifies the need to address issues about the adequacy of technological assessment and patient selection as well as the morbidity of those who undergo these procedures.

Assessment of neurosurgical outcome in children prenatally diagnosed with myelomeningocele and development of a protocol for fetal surgery to prevent hydrocephalus

INTRODUCTION

Prenatal diagnosis of myelomeningocele (MMC) has permitted a better planning for optimum management of the disease. More recently, it has allowed for a possible intrauterine repair of the spinal defect.

OBJECTIVE

To describe neurosurgical outcome in children with myelomeningocele and follow-up at a referral center in Fetal Medicine. Patients were characterized for the development of a protocol suitable for fetal surgery, and fetuses who were possible candidates for intrauterine surgery were identified.

MATERIALS AND METHODS

A retrospective descriptive analysis was performed of 98 cases of fetal myelomeningocele, seen at CAISM-UNICAMP, from January 1994 to December 2002, identifying cases with a possible indication for fetal surgery.

RESULTS

Mean gestational age at diagnosis was 29 weeks (17-39); level of lesion was above the sacral region in 92.84%; association with hydrocephalus occurred in 78.57%. During clinical course, 82.5% of patients had neurogenic bladder and 60% had neural and mental deficits. Potential intrauterine repair rate was 11.57%, using criteria from the protocol developed in our service.

CONCLUSION

Myelomeningocele is associated with severe and frequent sequelae. In virtually 12% of our cases, fetal surgery could have been offered as a therapeutic option.

Successful developmental outcome in intrauterine myelomeningocele repair

INTRODUCTION

Myelomeningocele (MM) is one of the forms of dysraphism. Hydrocephalus secondary to Arnold-Chiari (AC) malformation is responsible for the morbidity and mortality of the disease. The intrauterine repair of MM may reverse AC and limit hydrocephalus progression.

OBJECTIVE

The aim of this work is to report the successful outcome of a case of intrauterine correction of MM, with favorable evolution and birth at 36 weeks of pregnancy.

CASE REPORT

KCMC, 19 years old, was submitted to intrauterine repair of MM at 24 weeks of gestational age after approval by the family and the Research Ethics Committee of the School of Medical Sciences-UNICAMP.

CONCLUSION

Although it is not the standard option for surgical correction, selected MM cases with early fetal diagnosis may be eligible for intrauterine repair, when there is consensus with the Research Ethics Committees and family members.

Reclosure of surgically induced spinal open neural tube defects by the intraamniotic injection of human embryonic stem cells in chick embryos 24 hours after lesion induction

OBJECT

The authors previously reported that human embryonic stem cells (hESCs) injected into the amniotic cavity of chick embryos immediately after neural tube incision in a surgically induced spinal open neural tube defect (ONTD) model promote the reclosure capacity of neural tubes. To simulate more closely the clinical situation of human ONTDs, in which a substantial time period elapses before the prenatal diagnosis of spinal ONTDs, the authors investigated whether this reclosure capacity remains enhanced by the intraamniotic injection of hESCs at 24 hours after ONTD induction.

METHODS

One hundred twenty-two chick embryos with ONTDs were randomly assigned to two groups: the control group (59 embryos) and the hESC-injection group (hESC group, 63 embryos). After the neural tubes of both groups had been opened, the hESC group underwent direct intraamniotic injection with hESCs marked with an enhanced green fluorescent protein at 24 hours after ONTD induction. The lengths of the remnant ONTDs were measured and the presence of hESCs was determined at 4, 6, and 8 days after ONTD induction. No difference in survival rates was observed between the two groups. The mean length of the ONTDs, adjusted for body length at the time of death and initial lesion length, was significantly shorter in the hESC group than in the control group (p < 0.001). No hESCs were found within reclosed neural tubes; rather, they covered the defect area during the reclosure process.

CONCLUSIONS

The authors demonstrate that hESCs injected into the amniotic cavity at 24 hours after ONTD induction enhance reclosure ability in chick embryos.

Percutaneous Fetoscopic Patch Coverage of Spina Bifida Aperta in the Human – Early Clinical Experience and Potential

OBJECTIVE

The current operative approach for fetal repair of spina bifida aperta requires maternal laparotomy and hysterotomy. Following technical feasibility studies in sheep, we performed percutaneous fetoscopic patch coverage of this lesion in 3 human fetuses between 23 + 4 and 25 + 3 weeks of gestation.

METHODS AND RESULTS

Whereas the patch detached in the first case 3 weeks after the procedure, it covered the exposed neural tissue in the 2 other fetuses beyond their delivery. Two of the three children survived, but 1 unexpectedly died from a ventilation problem in its 3rd week of life. In 1 of the 2 survivors, ventriculoperitoneal shunt insertion was delayed.

CONCLUSIONS

Percutaneous fetoscopic patch coverage of spina bifida aperta is feasible in human fetuses and offers a substantial reduction of maternal trauma compared to open fetal repair. Further clinical experience is now required before the efficacy of the new approach to protect the exposed neural tissue from mechanical and chemical damage and to improve hindbrain herniation can be evaluated.

Abruptio Placentae during Fetal Myelomeningocele Repair

Myelomeningocele (MM) is a congenital neural tube defect with serious consequences, including hydrocephaly. An important hope for intrauterine repair is that hydrocephaly may be prevented by reversing the Arnold-Chiari malformation. Three medical centers in the United States are doing trials with this objective. We describe an intrauterine correction of MM in a Brazilian research center of fetal medicine, which resulted in abruptio placentae and fetal death, to illustrate factors that influence fetal-maternal risks during this surgical procedure.

Fetal anal incontinence evaluated by amniotic fluid digestive enzyme assay in myelomeningocele spina bifida

The goals of this study were to determine whether anal sphincter dysfunction in spina bifida develops during fetal life or after birth and whether it reflects the severity of spina bifida and therefore can be used as a criterion to select the cases that could benefit from in uterosurgery. Total protein and digestive enzyme activities [gamma-glutamyl transpeptidase (GGTP), aminopeptidase M (AMP), and alkaline phosphatase isoenzymes including the intestinal form (iALP)] were assayed retrospectively in amniotic fluid from 80 myelomeningocele spina bifida cases without unrelated associated malformation (gestational age 14-33 wk). A normal enzyme activity profile was observed in 46 of the 80 cases. Two abnormal profiles were observed: 1) bilious vomiting, characterized by abnormally high GGTP and AMP activities but normal iALP, and 2) digestive enzyme leakage, characterized by abnormally high activities of GGTP, AMP, and iALP, typical of anal incontinence. No relation was observed between these enzyme activity profiles and the different secondary signs of spina bifida or the level of the damage. In conclusion, anal sphincter dysfunction in spina bifida revealed by amniotic fluid digestive enzyme activities occurred before 24 wk in fetal life in 28.7% of cases. This criterion may be indicative of the severity of spina bifida and therefore perhaps could be used to select cases that are suited to in utero surgery. It could also be used to establish the potential benefit of this surgery in fecal incontinence.

In utero Repair of an Experimental Neural Tube Defect in a Chronic Sheep Model Using Biomatrices

OBJECTIVE

Persistent exposure of the unprotected spinal cord to amniotic fluid and the uterine wall can lead to progressive damage of neural tissue in case of a myelomeningocele (two-hit hypothesis). The aim of this study was to evaluate whether in utero repair of an experimental neural tube defect in a fetal lamb could protect neural tissue from secondary injury and save neurologic functions after birth.

METHODS

In 19 fetal lambs, a neural tube defect was created at 79 days' gestation. In 12 lambs the defect was covered either with a novel, molecular defined collagen-based biocompatible and biodegradable matrix (UMC) or with a small intestinal submucosa (SIS) biomatrix (Cook) or by closing the skin over the defect.

RESULTS

All lambs with the defect covered showed no or minor neurologic morbidity in contrast to the lambs with the defect uncovered in which major neurologic morbidity was seen.

CONCLUSIONS

These results demonstrate that long-term exposure of the open spinal cord to the intrauterine environment can lead to damage of neural tissue and, consequently loss of neurologic functions and that coverage of the defect can lead to a better neurologic outcome. Furthermore, we could show that a UMC biomatrix and an SIS biomatrix are useful for in utero coverage of a surgically created neural tube defect in our model.

Fetoscopic surgery: where are we today?

PURPOSE OF REVIEW

Since the early 1990s, advances in endoscopic equipment and the commercial availability of micro-catheters, mini-balloons, tiny laser fibers and other ingenious tools have set the trend toward the development of minimally invasive fetoscopic surgical techniques for the treatment of some congenital malformations that progress in severity over the course of gestation and may destroy entire organ systems of the unborn. The purpose of this review is to provide a state-of-the-art overview of these new procedures for the anesthesiologist.

RECENT FINDINGS

Procedures like diagnostic fetoscopies, laser coagulation of inter-twin placental vascular connections in twin-twin transfusion syndrome, fetal tracheal balloon occlusion in diaphragmatic hernia, laser perforation of posterior urethral valves, vocal cord division in congenital high-airway obstruction syndrome and most recently even coverage of spina bifida aperta can be performed entirely percutaneously using minimally invasive fetoscopic techniques. Careful selection of anesthetic methods and intensive maternal monitoring by the anesthesiology team are paramount to the success of these procedures, particularly in hemodynamically unstable fetuses or procedures that employ gas insufflation of the amniotic cavity.

SUMMARY

An increasing spectrum of congenital malformations can be treated by fetoscopic surgery. Compared to open fetal surgery, fetoscopic surgery results in significantly less maternal trauma. Like the open procedures, the efficacy of the fetoscopic procedures to improve fetal outcome over postnatal treatment strategies will have to be assessed in further studies under close supervision of committees for human research.

Developmental stages in the rabbit embryo: guidelines to choose an appropriate experimental model

Researchers involved in the field of congenital malformations are often forced to work on an animal model. Both accurate description of its normal development and comparative staging with human development will be mandatory. To complete the lacking medical literature, we herein provide such data for the rabbit model. Sampled rabbit embryos were staged using the Carnegie criteria, in order first to determine if they were consistent with the rabbit developmental pattern, and second to compare this pattern with the human one. Our results show a suitable comparison of rabbits and humans in early developmental stages, except for the neural growth.

Evolução de 58 fetos com meningomielocele e o potencial de reparo intra-útero

INTRODUÇÃO: O diagnóstico pré natal da meningomielocele (MM) permite melhor planejamento de sua abordagem e, mais recentemente , um possível reparo intra-útero. OBJETIVO: Descrição da evolução perinatal de fetos com MM, acompanhados em um centro de referência em Medicina Fetal, identificando os possíveis fetos candidatos à cirurgia intra-uterina. MÉTODO: Análise retrospectiva descritiva de 58 casos de MM fetal, atendidos no CAISM-UNICAMP, de janeiro de 1997 a dezembro de 2001, identificando-se os casos cuja indicação de cirurgia fetal seria possível. RESULTADOS: Média da idade gestacional ao diagnóstico de 29 semanas (17-39); nível da lesão acima da região sacral em 85%; associação com hidrocefalia em 86%; taxa de complicações cirúrgicas de 39%. Na evolução, 98% apresentaram bexiga neurogênica e 60% deficiência neuro-mental. O potencial reparo intra-útero foi de 42%. CONCLUSÃO: MM está associada a graves e frequentes sequelas. Quase um terço dos nossos casos poderiam ter tido a cirurgia fetal como opção terapêutica.

Intrauterine closure of myelomeningocele: an update

Preliminary evidence suggests that intrauterine myelomeningocele repair may benefit patients by reducing the both incidence of hydrocephalus and the severity of the Chiari malformation; however, this benefit remains unproved. Furthermore, the procedure entails substantial risks not associated with conventional therapy. A randomized controlled trial of intrauterine and conventional therapies is underway. This study should definitively establish the procedure-related risks and benefits. Regardless of the outcome, it is clear that the risks of intrauterine intervention need to be reduced before myelomeningocele, or other congenital malformations, can be effectively treated prior to birth. To that end, studies are being conducted to assess the potential advantages of applying state-of-the-art endoscopic techniques to intrauterine therapy. If benefit can be proven and risks reduced, intrauterine myelomeningocele repair has the potential to become the preferred therapy for patients suffering from this debilitating disease.

Fetal myelomeningocele repair: short-term clinical outcomes

OBJECTIVE

The study was undertaken to evaluate short-term clinical outcomes with antenatal myelomeningocele (MMC) repair.

STUDY DESIGN

Retrospective review of 50 fetuses that underwent open fetal MMC closure was performed. Inclusion criteria included less than 26 weeks' gestation, thoracic to S1 level defect, absent clubfoot deformity, Arnold-Chiari malformation, ventriculomegaly less than 17 mm, normal karyotype, and no other anomalies.

RESULTS

Perinatal survival was 94% (47/50 fetuses). Mean age at delivery was 34 weeks 3 days. All fetuses demonstrated reversal of hindbrain herniation. Forty-three percent of the 50 fetuses have required ventriculoperitoneal shunting compared with 100% thoracic, 88% lumbar, and 68% sacral (85% overall) in 297 historic controls. Better-than-predicted leg function was seen in 57% of thoracic and lumbar level lesion patients.

CONCLUSION

Early experience with fetal MMC repair suggests a decreased need for ventriculoperitoneal shunting, arrest or slowing of progressive ventriculomegaly, and consistent resolution of hindbrain herniation. However, further long-term follow-up is needed to evaluate neurodevelopment and bladder and bowel function.

Intrauterine myelomeningocele repair

Preliminary studies have suggested that IUMR reduces the incidence of shunt-dependent hydrocephalus and the severity of the Chiari malformation. An RCT is in progress to confirm these results. Future efforts will revolve around refinement of the procedure with the goal of reducing risk. Robot-assisted surgery holds the promise of achieving this goal. If it is successful. IUMR might well become the standard therapy for myelomeningocele, resulting in a significant reduction in the devastating morbidity associated with this disease.

The Arnold-Chiari type II malformation at midgestation

The Arnold-Chiari malformation type II (ACMII) is reported to be reversible after closure of a myelomeningocele at midgestation. To elucidate the developmental state of the ACMII malformation at the approximate time fetal surgery is performed, the ACMII of a 20-week human fetus was investigated in vitro using high-field magnetic resonance microscopy at 9.4 T and compared with the hindbrain of a neurologically intact fetus of the same gestational age. Up to 20 weeks of gestation, the developmental failures caused by the early embryonic herniation of the posterior fossa contents are the dominant feature of fetal ACMII, but after 20 weeks, the accelerated and disproportionate growth of the cerebellum dominates. As midgestational surgery stops the leakage of cerebrospinal fluid, the posterior fossa will expand in time to allow further normal growth of both the cerebellum and brain stem. Some early developmental anomalies already present in the primitive rhombencephalon due to early embryonic hindbrain herniation as well as some intra-axial anomalies are probably not reversible.

Congenital craniopharyngioma: a role for imaging in the prenatal diagnosis and treatment of an uncommon tumor

Ultrasonography and magnetic resonance imaging performed upon a male fetus at 32 and 36 weeks gestation, respectively, revealed a large suprasellar mass. A male newborn, delivered at 37 weeks, required ventilatory assistance at birth and subsequently developed myoclonic seizures, hypertension, and bradycardia. The intracranial mass was felt to be inoperable and the patient expired shortly after support was withdrawn. Autopsy results were consistent with a congenital craniopharyngioma. We discuss the differential diagnosis for this mass lesion based on prenatal imaging as well as distinguishing features on imaging studies that may aid in the prenatal diagnosis and treatment of this benign tumor.

History of fetal diagnosis and therapy: Children's Hospital of Philadelphia experience

Since its inception in 1995, the mission of the Center for Fetal Diagnosis and Treatment at the Children's Hospital of Philadelphia (CHOP) has been to provide comprehensive, multidisciplinary expertise in all facets of prenatal diagnosis, reproductive genetics, and prenatal, perinatal, and postnatal treatment for abnormal fetuses. Most of the authors were trained and/or served on faculty at centers in San Francisco (N.S.A., A.W.F., T.M.C., L.J.H.) or Detroit (A.W.F, M.P.J.). Accurate prenatal detection by serial sonographic study and the development of ultrafast magnetic resonance imaging (MRI) scanners has permitted delineation of the natural history of anatomic malformations. Definition of the pathophysiological features that affect clinical outcome and formulation of management based on prognosis has allowed families to make informed decisions. Outcomes have been improved through carefully planned and coordinated perinatal management. In some cases of life-threatening or severely debilitating defects, prenatal surgery has been offered.

In vitro high-field magnetic resonance imaging-documented anatomy of a fetal myelomeningocele at 20 weeks' gestation. A contribution to the rationale of intrauterine surgical repair of spina bifida

OBJECT

It remains uncertain if closure of a myelomeningocele at midgestation changes the neurological condition at birth in an infant born with spina bifida. The authors conducted a study to provide a detailed analysis of the morphology of the spinal cord with the myelomeningocele at the time fetal surgery usually is performed.

METHODS

The myelomeningocele of a 20-week-gestation-age fetus was examined, and data were compared with those obtained in a neurologically intact specimen of the same age. In vitro high-field 9.4-tesla magnetic resonance (MR) microscopy was used to examine the fetal material. High-field MR spectroscopy provided images in the three orthogonal planes with a resolution comparable with low-power optical microscopy. The authors observed that the fetal cord of the myelomeningocele specimen was tapered and tethered at S3-4 while the conus medullaris in the normal fetus reaches L-4. No neurulation defects were noted. The axial MR images clearly revealed the nonfusion of the mesodermal structures. The absence of neurulation defects suggests that at least in some cases of spina bifida the spinal cord initially is well developed but is damaged later on chemically and mechanically. This might be an argument in favor of intrauterine myelomeningocele repair. By 20 weeks' gestation, however, the deformation of the cord inside the myelomeningocele is severe. An optimization of the preoperative assessment by means of MR imaging therefore might be considered a valuable contribution to intrauterine surgery. The in vitro high-field MR microscopic findings of this study could be used as references for clinical intrauterine MR imaging.

CONCLUSIONS

The detailed in vitro high-field MR analysis of a 20-week-gestation-age fetus with spina bifida demonstrated that an improvement of the preoperative intrauterine imaging should be pursued to detect those cases without neurulation defects and with minimal deformation of the spinal cord.

Correction of hindbrain herniation and anatomy of the vermis after in utero repair of myelomeningocele in sheep

BACKGROUND/PURPOSE

In utero repair of myelomeningocele (MMC) in humans spares distal neurologic function, reverses the hindbrain herniation component of the Arnold-Chiari II malformation (ACM), and reduces the rate of postnatal shunt placement. The authors hypothesized that extravasation of cerebrospinal fluid (CSF) from the lumbar spinal cord results in herniation. This hypothesis was tested by assessing the impact of a spinal cord myelotomy on hindbrain anatomy in fetal sheep.

METHODS

A MMC lesion was created surgically in 34 fetal sheep at 75 days' gestation by excision of the L1-L5 lamina, the exposed dura, and surrounding tissues. A lumbar level myelotomy was performed in 28 of the 34 fetuses to open the central canal of the spinal cord to enhance egress of CSF through the MMC defect and potentially induce hindbrain herniation. At 102 days' gestation, a repair of the MMC lesion was performed in 14 fetuses with a myelotomy. Fetuses underwent autopsy at 102, 114, 120, or 140 days' gestation. Control animals underwent 2 unrelated fetal surgical procedures at approximately 70 and 110 days' gestation. The incidence of hindbrain herniation, ventricular size, biparietal diameter, brain weight, and brain anatomy were compared between the different animal groups.

RESULTS

After MMC creation, significant cerebellar tonsillar herniation was observed in 85% of fetuses that underwent creation of a myelotomy; none of the lambs without a myelotomy (n = 6) had hindbrain herniation. At autopsy, cerebellar tonsillar herniation was present at the time of MMC repair (102 days' gestation), 2 weeks after MMC repair, but was reversed 3 weeks post-MMC repair. At birth, tonsillar herniation was absent, and hindbrain anatomy was restored in 88% of the fetuses with a myelotomy that underwent fetal MMC repair. No significant differences in brain weight and ventricular size was observed between animals with and without MMC repair.

CONCLUSIONS

Adding a myelotomy to the sheep model of MMC leads to hindbrain herniation that is similar to that observed in the human ACM. These experiments support the hypothesis that leakage of CSF through the exposed central canal alters the normal CSF hydrodynamics, resulting in cerebellar tonsillar herniation. Fetal MMC repair reverses hindbrain herniation and restores gross anatomy of the vermis.

The effect of intrauterine myelomeningocele repair on the incidence of shunt-dependent hydrocephalus

BACKGROUND

Intrauterine myelomeningocele repair (IUMR) was first successfully performed in 1997. Preliminary reports suggest that this procedure reduces the incidence of shunt-dependent hydrocephalus when compared to conventional postnatal therapy. However, the existing cohort of IUMR patients has not yet been systematically compared to a comparable group of conventionally treated controls.

METHODS

Patients 1 year old or greater who had undergone IUMR at either Vanderbilt University or the Children's Hospital of Philadelphia (CHOP) were compared to a group of conventionally treated historical controls treated and followed at CHOP. In order to measure any differences between the groups, patients were stratified according to the level of the myelomeningocele lesion and the gestational age at the time of IUMR.

RESULTS

One hundred and four IUMR patients were compared to 189 conventionally treated controls. IUMR resulted in statistically significant reductions in the incidence of shunt-dependent hydrocephalus at both lumbar and sacral lesion levels. When lumbar lesion levels were further stratified, from L1 to L5, it appeared that the benefit of IUMR was statistically significant only at levels below L2. Other factors with a significant impact on hydrocephalus were estimated gestational age and ventricular size at the time of surgery. In particular, statistically significant differences compared to controls were seen in the younger (< or =25 weeks) group but not in the older (>25 weeks) group.

CONCLUSIONS

IUMR appears to substantially reduce the incidence of shunt-dependent hydrocephalus when compared to conventional treatment even when lesion level is taken into account. Patients with lesions above L3 may not share in this benefit. IUMR cannot be justified in fetuses older than 25 weeks of gestation. Additional improvements might be obtained by further reducing the average age at which fetuses are operated upon. It remains to be determined whether this benefit outweighs the potential risks of intrauterine surgery.

Audit of prenatal and postnatal diagnosis of isolated open spina bifida in three university hospitals in The Netherlands

OBJECTIVE

To audit the current Dutch policy of prenatal detection of isolated open spina bifida based on offering detailed ultrasound examination only on indication.

METHODS

A retrospective analysis of prenatally diagnosed isolated spina bifida cases and of newborns diagnosed with this condition was carried out in three university hospitals. The data were collected from databases and clinical records of the departments of prenatal diagnosis, obstetrics, neonatology, child neurology and neurosurgery of the three centers.

RESULTS

Between January 1996 and December 1999, 88 cases of isolated open spina bifida were diagnosed prenatally by ultrasound investigation. Thirty-eight cases (43%) were diagnosed before the 24th week of gestation. Of these, 35 (92%) ended in termination of the pregnancy at the parents' request. Of the remaining 50 cases (57%) diagnosed after the 24th week of gestation, eight (16%) pregnancies were terminated beyond the legal limit for termination due to the severity of the condition. Of the 88 cases of isolated spina bifida, 25 infants (28%) were still alive at the age of 4 years. In the same audit period 112 newborn infants with isolated open spina bifida were admitted to the neonatology, child neurology, or neurosurgery ward of the three centers. Of these cases, 47 (42%) had been diagnosed prenatally and 65 (58%) were an unexpected finding at birth. In 24 infants (21%) surgical treatment was withheld because of the severity of the condition and predicted poor outcome, whereas the remaining 88 infants (79%) underwent surgical repair.

CONCLUSION

The current practice in The Netherlands of offering ultrasound screening to high-risk patients only leads to the early detection of a minority of cases of spina bifida. Most cases are diagnosed either after the 24th week of gestation or they remain undiagnosed until after birth. When spina bifida is diagnosed before the 24th week of gestation the vast majority of parents opt for termination. In order to reduce the birth prevalence of spina bifida in The Netherlands the introduction of a policy of routine ultrasound screening should be considered.

Primary myelomeningocele closure and consequences

PURPOSE OF REVIEW

Myelomeningocele, the most frequently occurring open neural tube defect, requires lifelong care of the patient by medical professionals and by relatives. A basic understanding of the neurosurgical measures that have to be taken in the newborn, the infant, the child and the adult is important also for physicians of other disciplines involved in the treatment of patients with myelomeningocele.

RECENT FINDINGS

The most recent topic broadly discussed in this context is the role of foetal neurosurgery for closure of the neural tube defect. There is ongoing debate as to whether the beneficial postnatal effects of a prenatal operation in the unborn foetus outweighs the possible complications for the mother as well as the child.

SUMMARY

As some of the problems associated with myelomeningocele occur only later in life, it will still take many years until the beneficial, as well as the adverse, effects of prenatal neurosurgical procedures can be evaluated.

Prenatal evaluation for fetal surgery

The selection of fetuses that may benefit with in utero surgery is being developed. Noninvasive and invasive prenatal diagnosis techniques are utilized to try and gain as much knowledge about the fetus so that the appropriate counseling of parents can be undertaken. The most common invasive techniques are amniocentesis and chorionic villus sampling for fetal karyotyping and genetic diagnosis. Noninvasive techniques include ultrasound (2D and 3D), fetal echocardiography and magnetic resonance imaging. Additional techniques such as specific Doppler evaluation of vascular components, new techniques to look at fetal electrocardiograms and the use of computer tomography are also considered. The most common conditions for which in utero fetal surgery is also being considered are twin to twin transfusion syndrome, myelomeningocele, sacrococcygeal teratoma, cystic adenomatoid malformation of the lung with fetal hydrops and other monochorionic twin abnormalities (severe discordant birth defects or twin reversal arterial perfusion sequences). Ongoing evaluation of the sensitivity, specificity, positive and negative predicted values of these evaluation tools is required so that appropriate selection of fetuses for the surgery can be made.

Advances in fetal and neonatal surgery for gastrointestinal anomalies and disease

The last decade has seen considerable improvement in the understanding and treatment of neonatal surgical disorders. Translation of basic molecular biology research to clinical practice has directly improved the understanding and treatment of a number of congenital, developmental disorders, such as Hirschsprung's disease and congenital hyperinsulinism. Miniaturized instruments and improved optics have permitted increased use of videoscopic and minimally invasive techniques to even the smallest infants. Continued improvements in prenatal imaging will permit enhanced understanding of the prenatal natural history of congenital structural disorders and the development of more specific therapies. Finally, rigorous clinical research tools have begun to be applied to rare pediatric surgical disorders with the use of organized multicenter trials. It is an exciting time for all involved in the care of neonates.