Prenatal Repair of Myelomeningocele and School-age Functional Outcomes

Preliminary Evaluation of a Novel Fetal Guinea Pig Myelomeningocele Model

Introduction

Translational models of myelomeningocele (MMC) are needed to test novel in utero interventions. An ideal animal model for MMC has locomotor function at birth and is low cost enough to allow for high throughput. The rat MMC model is limited by immature locomotor function at birth. The ovine MMC model is a costly surgical model. Guinea pigs are uniquely suited for an MMC model being a small animal model with locomotor function at birth. We aimed to develop a retinoic acid (RA) model of MMC in the guinea pig and to evaluate if pregnant guinea pigs could tolerate uterine manipulation.

Methods

Time-mated Dunkin Hartley guinea pig dams were dosed with 60 mg/kg of RA between gestation age (GA) 12 and 15 days in the development of an RA model. Fetuses were grossly evaluated for MMC lesions at Cesarean section after GA 31 days. Evaluation of the ability of pregnant guinea pig dams to tolerate uterine surgical intervention was performed by hysterotomy of a separated group of time-mated guinea pigs at GA 45, 50, and 55.

Results

Forty-two pregnant guinea pigs were dosed with RA, with a total of 189 fetuses. The fetal demise rate was 38% (n = 71). A total of 118 fetuses were viable, 83% (n = 98) were normal fetuses, 8% (n = 10) had a neural tube defect, and 8% (n = 10) had a hematoma or other anomalies. No fetuses developed an MMC defect. None of the fetuses that underwent hysterotomy survived to term.

Conclusion

RA dosed at 60 mg/kg in guinea pigs between GA 12 and 15 did not result in MMC. Dunkin Hartley guinea pigs did not tolerate a hysterotomy near term in our surgical model. Further work is needed to determine if MMC can be induced in guinea pigs with alternate RA dosing.

Fetal myelomeningocele repair: a narrative review of the history, current controversies and future directions

Fetal surgery is a relatively new field of medicine. The purpose of this narrative review is to present the history of how fetal surgery became the standard of care for myelomeningocele (MMC), the current controversies of this treatment, and active areas of research that may change how MMC is treated. Fetal surgery for MMC emerged out of the University of California, San Francisco in the 1980s in the laboratory of Dr. Michael Harrison. Initial research focused on testing the hypothesis that the in utero repair of MMC could improve outcomes in the ovine model. Evidence from this model suggested that in utero repair decreases the secondary damage to the exposed neural tissue and improves post-natal neurologic outcomes, opening the door for human intervention. This was followed by the Management of Myelomeningocele Study (MOMS), which was a multicenter randomized controlled trial comparing the prenatal versus postnatal MMC repair. The MOMS trial was stopped early due to the improved outcomes of the prenatal repair, establishing the open fetal MMC repair as the standard of care. Since the MOMS trial, two primary areas of controversy have arisen: the operative approach and criteria for the repair. The three operative approaches include open, endoscopic and a hybrid approach combining open and endoscopic. Several of the inclusion and exclusion criteria from the MOMS trial have been challenged, to include body mass index, gestational diabetes, other fetal abnormalities, maternal infections and Rh alloimmunization. New areas of research have also emerged, exploring cell based therapies to improve fetal outcomes, alternatives to fetal surgery and alternatives to primary skin closure of the fetus.

Open fetal surgery for myelomeningocele repair in France

INTRODUCTION

Open fetal myelomeningocele (MMC) surgery is currently the standard of care option for prenatal MMC repair. We described the population referred to our center and reviewed outcome after open fetal MMC repair.

MATERIAL AND METHODS

All patients referred to our center for MMC were reviewed from July 2014 to June 2020. For all the patients who underwent fetal MMC repair, surgical details, maternal characteristics and data from the neonatal to the three-years-old evaluations were collected.

RESULTS

Among the 126 patients referred to our center, 49.2% were eligible and 27.4% (n = 17) of them underwent fetal MMC repair. Average gestational age at fetal surgery was 24⁺⁶ weeks. There was no case of fetal complication and the only maternal complication was one case of transfusion. We recorded 70% of premature rupture of membranes and 47% of premature labor. Average gestational age at delivery was 34⁺² weeks and no patient delivered before 30 weeks. There was no case of uterine scar dehiscence or maternal complication during cesarean section. After birth, 59% of the children had a hindbrain herniation reversal. At 1-year-old, 42% were assigned a functional level of one or more better than expected according to the prenatal anatomic level and 25% required a ventriculoperitoneal shunt. At 3-year-old, all the children attended school and 75% were able to walk with orthotics or independently.

CONCLUSION

Open fetal surgery enables anatomical repair of the MMC lesion, a potential benefit on cerebral anomalies and motor function, with a low rate of perinatal and maternal complications.

Fetoscopic myelomeningocoele closure: Is the scientific evidence enough to challenge the gold standard for prenatal surgery?

Since the completion of the Management of Myelomeningocoele Study, maternal-fetal surgery for spina bifida has become a valid option for expecting parents. More recently, multiple groups are exploring a minimally invasive approach and recent outcomes have addressed many of the initial concerns with this approach. Based on a previously published framework, we attempt to delineate the developmental stage of the surgical techniques. Furthermore, we discuss the barriers of performing randomized controlled trials comparing two surgical interventions and suggest that data collection through registries is an alternative method to gather high-grade evidence.

Prenatal Repair and Physical Functioning Among Children With Myelomeningocele: A Secondary Analysis of a Randomized Clinical Trial

IMPORTANCE

The Management of Myelomeningocele Study (MOMS), a randomized clinical trial of prenatal vs standard postnatal repair for myelomeningocele, found that prenatal repair reduced hydrocephalus and hindbrain herniation and improved motor function in children aged 12 to 30 months. The Management of Myelomeningocele Study Follow-up (MOMS2) was conducted in children at ages 5 to 10 years. The primary (neurocognitive) outcome has already been reported.

OBJECTIVE

To determine whether MOMS2 participants who had prenatal repair have better physical functioning than those with postnatal repair.

DESIGN, SETTING, AND PARTICIPANTS

Participants from MOMS were recruited for participation in the follow-up study, MOMS2, conducted from April 9, 2012, to April 15, 2017. For this secondary analysis of the randomized clinical trial, trained examiners without knowledge of the treatment group evaluated the physical characteristics, self-care skills, neurologic function, and mobility of the children. Physical functioning outcomes were compared between the prenatal and postnatal repair groups. MOMS2 was conducted at the same 3 clinical sites as MOMS. Home visits were conducted for families who were unable to travel to one of the clinical sites. Of the 161 children with myelomeningocele aged 5 to 10 years old enrolled in MOMS2, 154 had a physical examination and were included in the analyses.

EXPOSURES

Prenatal repair of myelomeningocele.

MAIN OUTCOMES AND MEASURES

Prespecified secondary trial outcomes of self-care skills, functional mobility, walking skills, and motor level.

RESULTS

This analysis included 78 children with postnatal repair (mean [SD] age, 7.4 [2.1] years; 50 girls [64.1%]; 69 White children [88.5%]) and 76 with prenatal repair (mean [SD] age, 7.5 [1.2] years; 43 boys [56.6%]; 70 White children [92.1%]). Children in the prenatal repair group were more competent with self-care skills (mean [SD] percentage of maximum FRESNO Scale score, 90.8% [9.6%] vs 85.5% [17.6%]) and were commonly community ambulators per the Modified Hoffer Classification (51.3% prenatal vs 23.1% postnatal; adjusted relative risk [aRR] for sex, 1.70; 95% CI, 1.23-2.34). Children with prenatal repair also performed the 10-m walk test 1 second faster (difference in medians, 1.0; 95% CI, 0.3-1.7), had better gait quality (adjusted mean difference for home distances of 5 m, 1.71; 95% CI, 1.14-2.54), and could perform higher-level mobility skills (adjusted mean difference for motor total, 5.70; 95% CI, 1.97-11.18). Children in the prenatal repair group were less likely to have a motor function level worse than their anatomic lesion level (aRR, 0.44; 95% CI, 0.25-0.77).

CONCLUSIONS AND RELEVANCE

This secondary analysis of a randomized clinical trial found that the physical functioning benefits of prenatal repair for myelomeningocele reported at age 30 months persisted into school age. These findings indicate the benefit of prenatal repair of myelomeningocele for school-aged children.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00060606.

Diffusion tensor imaging in children following prenatal myelomeningocele repair and its predictive value for the need and timing of subsequent CSF diversion surgery for hydrocephalus

OBJECTIVE

The aim of this study was to investigate diffusion tensor imaging (DTI), an objective and noninvasive neuroimaging technique, for its potential as an imaging biomarker to predict the need and timing of CSF diversion surgery in patients after prenatal myelomeningocele (MMC) repair.

METHODS

This was a retrospective analysis of data based on 35 pediatric patients after prenatal MMC repair (gestational age at birth 32.68 ± 3.42 weeks, range 24-38 weeks; 15 females and 20 males). A logistic regression analysis was used to classify patients to determine the need for CSF diversion surgery. The model performance was compared between using the frontooccipital horn ratio (FOHR) alone and using the FOHR combined with DTI values (the genu of the corpus callosum [gCC] and the posterior limb of the internal capsule [PLIC]). For patients who needed to be treated surgically, timing of the procedure was used as the clinical outcome to test the predictive value of DTI acquired prior to surgery based on a linear regression analysis.

RESULTS

Significantly lower fractional anisotropy (FA) values in the gCC (p = 0.014) and PLIC (p = 0.037) and higher mean diffusivity (MD) values in the gCC (p = 0.013) were found in patients who required CSF diversion surgery compared with those who did not require surgery (all p values adjusted for age). Based on the logistic regression analysis, the FOHR alone showed an accuracy of performance of 0.69 and area under the receiver operating characteristic curve (AUC) of 0.60. The performance of the model was higher when DTI measures were used in the logistic regression model (accuracy = 0.77, AUC = 0.84 for using DTI values in gCC; accuracy = 0.75, AUC = 0.84 for using DTI values in PLIC). Combining the DTI values of the gCC or PLIC and FOHR did not improve the model performance when compared with using the DTI values alone. In patients who needed CSF diversion surgery, significant correlation was found between DTI values in the gCC and the time interval between imaging and surgery (FA: ρ = 0.625, p = 0.022; MD: ρ = -0.6830, p = 0.010; both adjusted for age and FOHR).

CONCLUSIONS

The authors' data demonstrated that DTI could potentially serve as an objective biomarker differentiating patients after prenatal MMC repair regarding those who may require surgery for MMC-associated hydrocephalus. The predictive value for the need and timing of CSF diversion surgery is highly clinically relevant for improving and optimizing decision-making for the treatment of hydrocephalus in this patient population.

Fetal surgery for spina bifida in Zurich: results from 150 cases

PURPOSE

Over the past 10 years, over 150 fetal spina bifida surgeries were performed at the Zurich Center for Fetal Diagnosis and Therapy. This study looks at surrogates for success and failure of this approach.

METHODS

We focused on key outcome parameters including hydrocephalus shunt rate at one year, bladder control at 4, independent ambulation at 3 years, and maternal, fetal, and neonatal complications.

RESULTS

From the first 150 patients undergoing fetal surgery for spina bifida, 148 (98.7%) were included in the study. Maternal-fetal surgery was uneventful in 143/148 (97%) cases. Intraoperative problems included resuscitation in 4/148 fetuses (2.7%). 1/148 fetuses (0.7%) died on postoperative day 4. Maternal complications included chorioamniotic membrane separation in 22/148 (15%), lung embolism in 3/148 (2.1%), chorioamnionitis in 2/148 (1.4%), AV-block III and uterine rupture in 1/148 each (0.7%). 1/148 (0.7%) newborn death was recorded. Hindbrain herniation was identified preoperatively in 132/148 (90%) fetuses and resolved completely in 119/132 (90%). At one year, 39/106 (37%) children had required a CSF diversion. At 4 years, 4/34 patients (12%) had normal bladder control. At 3 years, 48/57 (84%) walked independently.

CONCLUSION

A majority of patients benefitted from prenatal intervention, in that the shunt rate was lower and the rates of continent and walking patients were higher than reported with postnatal care.

Functional Motor Skills in Children Who Underwent Fetal Myelomeningocele Repair: Does Anatomic Level Matter?

BACKGROUND

In this study, we evaluated children who underwent prenatal myelomeningocele (MMC) repair to investigate the influence of the anatomical level of the lesion on functional motor skills and congenital orthopedic malformations.

METHODS

This cross-sectional study evaluated children who underwent prenatal correction. The anatomical level of the lesion was classified by observing the magnetic resonance of the spine. The sensory/motor assessment was performed by physical examination to classify the status of ambulation, functional level, and functional performance according to chronological age using the Pediatric Evaluation of Disability Inventory (PEDI-CAT) scale.

RESULTS

One hundred cases were evaluated; for 60%, lesions were located in the upper lumbar region and for 40%, they were located in the lower lumbar and sacral regions. The functionality, measured by the PEDI-CAT scale, showed a normal average according to age (mean 50), with 71% of children being community ambulators. Congenital orthopedic malformations were also unrelated to the injury levels, except for knee dislocation in relation to upper lumbar injury. At the functional level, we observed that for the majority, the levels of function of at least 2 vertebrae were below the anatomical level.

CONCLUSIONS

There were no differences in functional motor skills, walking pattern, or congenital orthopedic malformation when compared with the anatomical level of injury in patients who underwent prenatal repair of MMC, except for congenital knee dislocation.

Open Fetal Microneurosurgery for Intrauterine Spina Bifida Repair

OBJECTIVES

The aim of the study was to describe the feasibility of open fetal microneurosurgery for intrauterine spina bifida (SB) repair and to compare perinatal outcomes with cases managed using the classic open fetal surgery technique.

METHODS

In this study, we selected a cohort of consecutive fetuses with isolated open SB referred to our fetal surgery center in Queretaro, Mexico, during a 3.5-year period (2016-2020). SB repair was performed by either classic open surgery (6- to 8-cm hysterotomy with leakage of amniotic fluid, which was replaced before uterine closure) or open microneurosurgery, which is a novel technique characterized by a 15- to 20-mm hysterotomy diameter, reduced fetal manipulation by fixing the fetal back, and maintenance of normal amniotic fluid and uterine volume during the whole surgery. Perinatal outcomes of cases operated with the classic open fetal surgery technique and open microneurosurgery were compared.

RESULTS

Intrauterine SB repair with a complete 3-layer correction was successfully performed in 60 cases either by classic open fetal surgery (n = 13) or open microneurosurgery (n = 47). No significant differences were observed in gestational age (GA) at fetal intervention (25.4 vs. 25.1 weeks, p = 0.38) or surgical times (107 vs. 120 min, p = 0.15) between both groups. The group with open microneurosurgery showed a significantly lower rate of oligohydramnios (0 vs. 15.4%, p = 0.01), preterm rupture of the membranes (19.0 vs. 53.8%, p = 0.01), higher GA at birth (35.1 vs. 32.7 weeks, p = 0.03), lower rate of preterm delivery <34 weeks (21.4 vs. 61.5%, p = 0.01), and lower rate of perinatal death (4.8 vs. 23.1%, p = 0.04) than the group with classic open surgery. During infant follow-up, the rate of hydrocephalus requiring ventriculoperitoneal shunting was similar between both groups (7.5 vs. 20%, p = 0.24). All patients showed an intact hysterotomy site at delivery.

CONCLUSION

Intrauterine spina repair by open fetal microneurosurgery is feasible and was associated with better perinatal outcomes than classic open fetal surgery.

Langzeitoutcome nach prä- vs. postnataler MMC-Operation

Die pränatale Korrektur einer Myelomeningozele (MMC) hat im Vergleich zum postnatalen Eingriff nachweisliche Vorteile: Die Patienten entwickeln im Kleinkindalter seltener einen Hydrozephalus, benötigen seltener einen Shunt und zeigen eine bessere motorische Entwicklung. Im Rahmen einer Nachbeobachtungsstudie prüften US-Wissenschaftler nun, ob diese Effekte bis ins Schulalter anhalten und inwiefern Unterschiede im adaptiven Verhalten bestehen.

Fetal surgery and neonatal ICU admissions

PURPOSE OF REVIEW

Fetal intervention is a dynamic field with wide-reaching implications on neonatal ICU admissions and the care of neonates with congenital anomalies. The aim of this review is to summarize recent advancements in fetal surgery and provide a broad understanding of how these topics interrelate.

RECENT FINDINGS

Advancements in prenatal imaging and diagnosis have dramatically expanded the indications for fetal intervention. Most recently, there has been a large focus on evaluating minimally invasive strategies of fetal intervention, notably fetoscopic surgery, and the use of stem cells for fetal treatment of myelomeningocele. With the advances in fetal intervention, neonatal care has adapted to the needs of these various patients to help improve the outcomes of this unique population.

SUMMARY

Fetal intevention relies on a multidisciplinary team from prenatal imaging and maternal fetal medicine to fetal surgery and postnatal subspecialty care, particuarly neonatology. Fetal intervention uniquely involves two patients, both mother and fetus, and therefore, has unique risks and considerations, particularly in the advancement of the field. As the number of conditions suited to fetal intervention grows, awareness and advancement of the postnatal intensive care necessary for these patients are essential.

New Trends in Fetal Anesthesia

Fetal anesthesia teams must understand the pathophysiology and rationale for the treatment of each disease process. Treatment can range from minimally invasive procedures to maternal laparotomy, hysterotomy, and major fetal surgery. Timing may be in early, mid-, or late gestation. Techniques continue to be refined, and the anesthetic plans must evolve to meet the needs of the procedures. Anesthetic plans range from moderate sedation to general anesthesia that includes monitoring of 2 patients simultaneously, fluid restriction, invasive blood pressure monitoring, vasopressor administration, and advanced medication choices to optimize fetal cardiac function.

Spinal Cord Injury in Myelomeningocele: Prospects for Therapy

Myelomeningocele (MMC) is the most common congenital defect of the central nervous system and results in devastating and lifelong disability. In MMC, the initial failure of neural tube closure early in gestation is followed by a progressive prenatal injury to the exposed spinal cord, which contributes to the deterioration of neurological function in fetuses. Prenatal strategies to control the spinal cord injury offer an appealing therapeutic approach to improve neurological function, although the definitive pathophysiological mechanisms of injury remain to be fully elucidated. A better understanding of these mechanisms at the cellular and molecular level is of paramount importance for the development of targeted prenatal MMC therapies to minimize or eliminate the effects of the injury and improve neurological function. In this review article, we discuss the pathological development of MMC with a focus on in utero injury to the exposed spinal cord. We emphasize the need for a better understanding of the causative factors in MMC spinal cord injury, pathophysiological alterations associated with the injury, and cellular and molecular mechanisms by which these alterations are induced.