In utero surgery rescues neurological function at birth in sheep with spina bifida

Thalamic connectivity topography in newborns with spina bifida: association with neurological functional level but not developmental outcome at 2 years

Spina bifida affects spinal cord and cerebral development, leading to motor and cognitive delay. We investigated whether there are associations between thalamocortical connectivity topography, neurological function, and developmental outcomes in open spina bifida. Diffusion tensor MRI was used to assess thalamocortical connectivity in 44 newborns with open spina bifida who underwent prenatal surgical repair. We quantified the volume of clusters formed based on the strongest probabilistic connectivity to the frontal, parietal, and temporal cortex. Developmental outcomes were assessed using the Bayley III Scales, while the functional level of the lesion was assessed by neurological examination at 2 years of age. Higher functional level was associated with smaller thalamo-parietal, while lower functional level was associated with smaller thalamo-temporal connectivity clusters (Bonferroni-corrected P < 0.05). Lower functional levels were associated with weaker thalamic temporal connectivity, particularly in the ventrolateral and ventral anterior nuclei. No associations were found between thalamocortical connectivity and developmental outcomes. Our findings suggest that altered thalamocortical circuitry development in open spina bifida may contribute to impaired lower extremity function, impacting motor function and independent ambulation. We hypothesize that the neurologic function might not merely be caused by the spinal cord lesion, but further impacted by the disruption of cerebral neuronal circuitry.

Duration of fetoscopic spina bifida repair does not affect the central nervous system in fetal lambs

BACKGROUND

Prenatal spina bifida aperta repair improves neurologic outcomes yet comes with a significant risk of prematurity and uterine scar-related complications. To reduce such complications, different fetoscopic techniques, for example, with varying numbers of ports, are being explored. This has an effect on the duration of the procedure, potentially affecting central nervous system development. Both the condition and anesthesia can affect the central nervous system, particularly the hippocampus, a region crucial for prospective and episodic memory. Previous animal studies have shown the potential influence of anesthesia, premature delivery, and maternal surgery during pregnancy on this area.

OBJECTIVE

This study aimed to compare the effects of 2- vs 3-port fetoscopic spina bifida aperta repair in the fetal lamb model using neuron count of the hippocampus as the primary outcome.

STUDY DESIGN

Based on the hippocampal neuron count from previous lamb experiments, we calculated that we required 5 animals per group to achieve a statistical power of ≥ 80%. A spina bifida aperta defect was developed in fetal lambs at 75 days of gestation (term: 145 days). At 100 days, fetuses underwent either a 2-port or 3-port fetoscopic repair. At 143 days, all surviving fetuses were delivered by cesarean delivery, anesthetized, and transcardially perfused with a mixture of formaldehyde and gadolinium. Next, they underwent neonatal brain and spine magnetic resonance imaging after which these organs were harvested for histology. Hippocampus, frontal cortex, caudate nucleus, and cerebellum samples were immunostained to identify neurons, astrocytes, microglia, and markers associated with cell proliferation, myelination, and synapses. The degree of hindbrain herniation and the ventricular diameter were measured on magnetic resonance images and volumes of relevant brain and medulla areas were segmented.

RESULTS

Both treatment groups included 5 fetuses and 9 unoperated littermates served as normal controls. The durations for both skin-to-skin (341±31 vs 287±40 minutes; P=.04) and fetal surgery (183±30 vs 128±22; P=.01) were longer for the 2-port approach than for the 3-port approach. There was no significant difference in neuron density in the hippocampus, frontal cortex, and cerebellum. In the caudate nucleus, the neuron count was higher in the 2-port group (965±156 vs 767±92 neurons/mm2; P=.04). There were neither differences in proliferation, astrogliosis, synaptophysin, or myelin. The tip of the cerebellar vermis was closer to the foramen magnum in animals undergoing the 2-port approach than in animals undergoing the 3-port approach (-0.72±0.67 vs -2.47±0.91 mm; P=.009). There was no significant difference in the ratio of the hippocampus, caudate nucleus, or cerebellar volume to body weight. For the spine, no difference was noted in spine volume-to-body weight ratio for the lower (L1-L2), middle (L3-L4), and higher (L5-L6) levels. Compared with controls, in repaired animals, the cerebellar vermis tip laid closer to the foramen magnum, parietal ventricles were enlarged, and medulla volumes were reduced.

CONCLUSION

In the experimental spina bifida fetal lamb model, a 2-port repair took 40% longer than a 3-port repair. However, there was no indication of any relevant morphologic differences in the fetal brain.

Caudal Fgfr1 disruption produces localised spinal mis-patterning and a terminal myelocystocele-like phenotype in mice

Closed spinal dysraphisms are poorly understood malformations classified as neural tube (NT) defects. Several, including terminal myelocystocele, affect the distal spine. We have previously identified a NT closure-initiating point, Closure 5, in the distal spine of mice. Here, we document equivalent morphology of the caudal-most closing posterior neuropore (PNP) in mice and humans. Closure 5 forms in a region of active FGF signalling, and pharmacological FGF receptor blockade impairs its formation in cultured mouse embryos. Conditional genetic deletion of Fgfr1 in caudal embryonic tissues with Cdx2Cre diminishes neuroepithelial proliferation, impairs Closure 5 formation and delays PNP closure. After closure, the distal NT of Fgfr1-disrupted embryos dilates to form a fluid-filled sac overlying ventrally flattened spinal cord. This phenotype resembles terminal myelocystocele. Histological analysis reveals regional and progressive loss of SHH- and FOXA2-positive ventral NT domains, resulting in OLIG2 labelling of the ventral-most NT. The OLIG2 domain is also subsequently lost, eventually producing a NT that is entirely positive for the dorsal marker PAX3. Thus, a terminal myelocystocele-like phenotype can arise after completion of NT closure with localised spinal mis-patterning caused by disruption of FGFR1 signalling.

Evolution and Variations of the Ovine Model of Spina Bifida

Spina bifida is the most common congenital anomaly of the central nervous system and the first non-fatal fetal lesions to be addressed by fetal intervention. While research in spina bifida has been performed in rodent, nonhuman primate, and canine models, sheep have been a model organism for the disease. This review summarizes the history of development of the ovine model of spina bifida, previous applications, and translation into clinical studies. Initially used by Meuli et al. [Nat Med. 1995;1(4):342-7], fetal myelomeningocele defect creation and in utero repair demonstrated motor function preservation. The addition of myelotomy in this model can reproduce hindbrain herniation malformations, which is the leading cause of mortality and morbidity in humans. Since inception, the ovine models have been validated numerous times as the ideal large animal model for fetal repair, with both locomotive scoring and spina bifida defect scoring adding to the rigor of this model. The ovine model has been used to study different methods of myelomeningocele defect repair, the application of various tissue engineering techniques for neuroprotection and bowel and bladder function. The results of these large animal studies have been translated into human clinical trials including Management of Meningocele Study (MOMS) trial that established current standard of care for prenatal repair of spina bifida defects, and the ongoing trials including the Cellular Therapy for In Utero Repair of Myelomeningocele (CuRe) trial using a stem cell patch for repair. The advancement of these life savings and life-altering therapies began in sheep models, and this notable model continues to be used to further the field including current work with stem cell therapy.

Advances in Fetal Surgical Repair of Open Spina Bifida

Spina bifida remains a common congenital anomaly of the central nervous system despite national fortification of foods with folic acid, with a prevalence of 2-4 per 10,000 live births. Prenatal screening for the early detection of this condition provides patients with the opportunity to consider various management options during pregnancy. Prenatal repair of open spina bifida, traditionally performed by the open maternal-fetal surgical approach through hysterotomy, has been shown to improve outcomes for the child, including decreased need for cerebrospinal fluid diversion surgery and improved lower neuromotor function. However, the open maternal-fetal surgical approach is associated with relatively increased risk for the patient and the overall pregnancy, as well as future pregnancies. Recent advances in minimally invasive prenatal repair of open spina bifida through fetoscopy have shown similar benefits for the child but relatively improved outcomes for the pregnant patient and future childbearing.

Neurogenic Lower Urinary Tract Dysfunction in Spinal Dysraphism: Morphological and Molecular Evidence in Children

Spinal dysraphism, most commonly myelomeningocele, is the typical cause of a neurogenic lower urinary tract dysfunction (NLUTD) in childhood. The structural changes in the bladder wall in spinal dysraphism already occur in the fetal period and affect all bladder wall compartments. The progressive decrease in smooth muscle and the gradual increase in fibrosis in the detrusor, the impairment of the barrier function of the urothelium, and the global decrease in nerve density, lead to severe functional impairment characterized by reduced compliance and increased elastic modulus. Children present a particular challenge, as their diseases and capabilities evolve with age. An increased understanding of the signaling pathways involved in lower urinary tract development and function could also fill an important knowledge gap at the interface between basic science and clinical implications, leading to new opportunities for prenatal screening, diagnosis, and therapy. In this review, we aim to summarize the evidence on structural, functional, and molecular changes in the NLUTD bladder in children with spinal dysraphism and discuss possible strategies for improved management and for the development of new therapeutic approaches for affected children.

Neuroprotection is improved by watertightness of fetal spina bifida repair in the sheep model

OBJECTIVES

A contributing factor to unsuccessful prenatal spina bifida aperta (SBA) repair via an open approach may be incomplete neurosurgical repair causing persistent in-utero leakage of cerebrospinal fluid (CSF) and exposure of the fetal spinal cord to amniotic fluid. We aimed to investigate the neurostructural and neurofunctional efficacy of watertight prenatal SBA repair in a validated SBA fetal lamb model.

METHODS

A well-powered superiority study was conducted in the validated SBA fetal lamb model (n = 7 per group). The outcomes of lambs which underwent watertight or non-watertight multilayer repair through an open approach were compared to those of unrepaired SBA lambs (historical controls) at delivery (term = 145 days). At ∼75 days, fetal lambs underwent standardized induction of lumbar SBA. At ∼100 days, they were assigned to an either watertight or non-watertight layered repair group based on an intraoperative watertightness test using subcutaneous fluorescein injection. At 1-2 days postnatally, as primary outcome, we assessed reversal of hindbrain herniation using magnetic resonance imaging (MRI). Secondary proxies of neuroprotection were: absence of CSF leakage at the repair site; hindlimb motor function based on joint-movement score, locomotor grade and Motor Evoked Potential (MEP); four-score neuroprotection scale, encompassing live birth, complete hindbrain herniation reversal, absence of CSF leakage and joint-movement score ≥ 9/15; and brain and spinal cord histology and immunohistochemistry. As the watertightness test cannot be used clinically due to its invasiveness, we developed a potential surrogate intraoperative three-score skin-repair-quality scale based on visual assessment of the quality of the skin repair (suture inter-run distance ≤ 3 mm, absence of tear and absence of ischemia), with high quality defined by a score ≥ 2/3 and low quality by a score < 2/3, and assessed its relationship with improved outcome.

RESULTS

Compared with unrepaired lambs, lambs with watertight repair achieved a high level of neuroprotection (neuroprotection score of 4/4 in 5/7 vs 0/7 lambs) as evidenced by: a significant 100% (vs 14%) reversal of hindbrain herniation on MRI; low CSF leakage (14% vs 100%); better hindlimb motor function, with higher joint-movement score, locomotor grade and MEP area under the curve and peak-to-peak amplitude; higher neuronal density in the hippocampus and corpus callosum; and higher reactive astrogliosis at the SBA lesion epicenter. Conversely, lambs with non-watertight SBA repair did not achieve the same level of neuroprotection (score of 4/4 in 1/7 lambs) compared with unrepaired lambs, with: a non-significant 86% (vs 14%) reversal of hindbrain herniation; high CSF leakage (43% vs 100%); no improvement in motor function; low brain neuron count in both the hippocampus and corpus callosum; and small spinal astroglial cell area at the epicenter. Both watertight layered repair and high (≥ 2/3) intraoperative skin-repair-quality score were associated with improved outcome, but the watertightness test and skin-repair-quality scale could not be used interchangeably due to result discrepancies.

CONCLUSIONS

Watertight layered fetal SBA repair is neuroprotective since it improves brain and spinal-cord structure and function in the fetal lamb model. This translational research has important clinical implications. A neurosurgical technique that achieves watertightness should be adopted in all fetal centers to improve neuroprotection. Future clinical studies could assess whether a high skin-repair-quality score (≥ 2/3) correlates with neuroprotection. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Motor function outcomes in children with open prenatal repair of Spina Bifida Aperta at 36-month follow-up: The Zurich cohort

PURPOSE

This study aimed to describe outcomes of motor function with a special focus on ambulation ability at 36 months among children with open prenatal repair of spina bifida aperta (SB).

METHODS

A prospective cohort study was conducted including 87 patients with open prenatal repair of SB at the investigating center born between 2010 and 2018. Anatomic lesion level and motor function level in the neonatal period, as well as motor function level, ambulation status, and use of orthotics and assistive devices at 36 months were assessed.

RESULTS

At 36 months, ambulation was assessed in 86 children; of those, 86% (n = 74) were ambulating. Independent of ambulation, orthotics were worn in 81.6% (71/87) and assistive devices in 47.1% (41/87). Children with a lower lumbar or sacral motor function level were the first to reach independent ambulation and were more likely to ambulate at 36 months than children with higher motor function levels (p = < .001). The anatomic lesion level determined on the neonatal MRI correlated with ambulation status at 36 months (p = < 0.001).

CONCLUSION

At 36 months, most children with open prenatal repair for SB showed favourable ambulation status. However, most still used assistive devices or orthotics. Anatomic lesion level on neonatal MRI, motor function level during the neonatal period, and motor function level at 36 months were associated with ambulation status at 36 months.

Fetal Surgery for Myelomeningocele: Neurosurgical Perspectives

More than 30 years have elapsed since it was recognised that folic acid supplementation could substantially reduce the risk of open neural tube defects (ONTDs). During that time, many countries have adopted policies of food fortification with demonstrable reduction in the incidence of both cranial and spinal ONTDs. Improved prenatal detection and termination has also resulted in a reduction in the number of affected live births. Nonetheless, in the USA about 1500 children, and in the UK around 500 children are born each year with myelomeningocele (MMC) and so the management of MMC and its complications continues to constitute a significant clinical workload for many paediatric neurosurgical units around the world.Until recently, the options available following antenatal diagnosis of MMC were termination of pregnancy or postnatal repair. As a result of the MOMS trial, prenatal repair has become an additional option in selected cases (Adzick et al., N Engl J Med 364(11):993-1004, 2011). Fetal surgery for myelomeningocele is now offered in more than 30 centres worldwide. The aim of this chapter is to review the experimental basis of prenatal repair of MMC, to critically evaluate the neurosurgical implications of this intervention and to describe the technique of 'open' repair, comparing this with emerging minimally invasive alternatives.

Modelling Neurological Diseases in Large Animals: Criteria for Model Selection and Clinical Assessment

Issue: The impact of neurological disorders is recognised globally, with one in six people affected in their lifetime and few treatments to slow or halt disease progression. This is due in part to the increasing ageing population, and is confounded by the high failure rate of translation from rodent-derived therapeutics to clinically effective human neurological interventions. Improved translation is demonstrated using higher order mammals with more complex/comparable neuroanatomy. These animals effectually span this translational disparity and increase confidence in factors including routes of administration/dosing and ability to scale, such that potential therapeutics will have successful outcomes when moving to patients. Coupled with advancements in genetic engineering to produce genetically tailored models, livestock are increasingly being used to bridge this translational gap. Approach: In order to aid in standardising characterisation of such models, we provide comprehensive neurological assessment protocols designed to inform on neuroanatomical dysfunction and/or lesion(s) for large animal species. We also describe the applicability of these exams in different large animals to help provide a better understanding of the practicalities of cross species neurological disease modelling. Recommendation: We would encourage the use of these assessments as a reference framework to help standardise neurological clinical scoring of large animal models.

Fetoscopic insufflation of heated-humidified carbon dioxide during simulated spina bifida repair is safe under controlled anesthesia in the fetal lamb

OBJECTIVE

To assess the safety of Partial-Amniotic-Insufflation-of-heated-humidified-CO₂ (hPACI) during fetoscopic spina bifida repair (fSB-repair).

METHOD

A simulated fSB-repair through an exteriorized uterus under hPACI was performed in 100-day fetal lambs (term = 145 days) under a laboratory anesthesia protocol (n = 5; group 1) which is known to induce maternal-fetal acidosis and hypercapnia. Since these may not occur clinically, we applied a clinical anesthesia protocol (n = 5; group 2), keeping maternal parameters within physiological conditions, that is, controlled maternal arterial carbon dioxide (CO2) pressure (pCO₂  = 30 mmHg), blood pressure (≥67 mmHg), and temperature (37.1-39.8°C). Our superiority study used fetal pH as the primary outcome.

RESULTS

Compared to group 1, controlled anesthesia normalized fetal pH (7.23 ± 0.02 vs. 7.36 ± 0.02, p < 0.001), pCO₂ (70.0 ± 9.1 vs. 43.0 ± 1.0 mmHg, p = 0.011) and bicarbonate (27.8 ± 1.1 vs. 24.0 ± 0.9 mmol/L, p = 0.071) at baseline. It kept them within clinically acceptable limits (pH ≥ 7.23, pCO₂  ≤ 70 mmHg, bicarbonate ≤ 30 mm/L) for ≥120 min of hPACI as opposed to ≤30 min in group one. Fetal pO₂ and lactate were comparable between groups and generally within normal range. Fetal brain histology demonstrated fewer apoptotic cells and higher neuronal density in the prefrontal cortex in group two. There was no difference in fetal membrane inflammation, which was mild.

CONCLUSION

Fetoscopic insufflation of heated-humidified CO₂ during simulated fSB-repair through an exteriorized uterus can be done safely under controlled anesthesia.

Long-term safety evaluation of placental mesenchymal stromal cells for in utero repair of myelomeningocele in a novel ovine model

PURPOSE

Augmentation of in utero myelomeningocele repair with human placental mesenchymal stromal cells seeded onto extracellular matrix (PMSC-ECM) improves motor outcomes in an ovine myelomeningocele model. This study evaluated the safety of PMSC-ECM application directly onto the fetal spinal cord in preparation for a clinical trial.

METHODS

Laminectomy of L5-L6 with PMSC-ECM placement directly onto the spinal cord was performed in five fetal lambs at gestational age (GA) 100-106 days. Lambs and ewes were monitored for three months following delivery. Lambs underwent magnetic resonance imaging (MRI) of the brain and spine at birth and at three months. All organs from lambs and uteri from ewes underwent histologic evaluation. Lamb spinal cords and brains and ewe placentas were evaluated for persistence of PMSCs by polymerase chain reaction for presence of human DNA.

RESULTS

MRIs demonstrated no evidence of abnormal tissue growth or spinal cord tethering. Histological analysis demonstrated no evidence of abnormal tissue growth or treatment related adverse effects. No human DNA was identified in evaluated tissues.

CONCLUSION

There was no evidence of abnormal tissue growth or PMSC persistence at three months following in utero application of PMSC-ECM to the spinal cord. This supports proceeding with clinical trials of PMSC-ECM for in utero myelomeningocele repair.

LEVEL OF EVIDENCE

N/A TYPE OF STUDY: Basic science.

Early childhood neurodevelopmental outcome after open prenatal spina bifida aperta repair

AIM

To investigate neurodevelopmental outcome of children with open prenatal spina bifida aperta (SBA) repair.

METHOD

Prenatal SBA repair was performed in 130 fetuses at the Zurich Center between 2010 and 2019. Seventy-seven children underwent 1 year assessment with the Griffiths Mental Developmental Scales (Griffiths) and 65 with the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III) at 2 years. Anatomical and functional level and ambulation status were assessed. Descriptive statistics and multiple linear regression analyses for risk factors were performed.

RESULTS

The Bayley-III cognition composite score in children with prenatal SBA repair was within normal limits but lower compared to population norms (mean=95.15, SD=14.683 vs norm=100, SD=15, p=0.01). Fine motor development (mean=9.58, SD=2.744, p=0.227) was typical while gross motor development was lower than the norm (mean=3.02, SD=2.758 vs norm=10, SD=3, p<0.001). Griffiths developmental quotient subscales correlated significantly with corresponding Bayley-III scores (all p<0.001, r=0.519-0.594). At 2 years, 50.8% could walk.

INTERPRETATION

Children with non-trial open prenatal SBA repair show favourable cognitive outcome in the low-average range at 1 and 2 years of age. While gross motor function remained delayed, fine motor function was age appropriate. The correlation between Griffiths and Bayley-III allows a prediction about neurodevelopmental outcome at the age of 1 year. What this paper adds Children with non-trial open prenatal spina bifida repair show favourable cognitive outcome. Gross motor function remains impaired, while fine motor function is age appropriate. At 2 years of age, 50.8% of children were walking. Neurodevelopmental testing correlated between 1 (Griffiths Mental Developmental Scales) and 2 (Bayley Scales of Infant and Toddler Development, Third Edition) years.

Allografts for Skin Closure during In Utero Spina Bifida Repair in a Sheep Model

Objectives: Use of off-label tissue graft materials, such as acellular dermal matrix (ADM), for in utero repair of severe spina bifida (SB), where primary skin layer closure is not possible, is associated with poor neurological outcomes. The cryopreserved human umbilical cord (HUC) patch has regenerative, anti-inflammatory, and anti-scarring properties, and provides watertight SB repair. We tested the hypothesis that the HUC is a superior skin patch to ADM for reducing inflammation at the repair site and preserving spinal cord function. Methods: In timed-pregnant ewes with twins, on gestational day (GD) 75, spina bifida was created without a myelotomy (functional model). On GD 95, repair was performed using HUC vs. ADM patches (randomly assigned) by suturing them to the skin edges. Additionally, full thickness skin closure as a primary skin closure (PSC) served as a positive control. Delivery was performed on GD 140, followed by blinded to treatment neurological assessments of the lambs using the Texas Spinal Cord Injury Scale (TSCIS) for gait, proprioception, and nociception. Lambs without spina bifida were used as controls (CTL). Ex vivo magnetic resonance imaging of spines at the repair site were performed, followed by quantitative pathological assessments. Histological assessments (blinded) included Masson’s trichrome, and immunofluorescence for myeloperoxidase (MPO; neutrophils) and for reactive astrocytes (inflammation) by co-staining vimentin and GFAP. Results: The combined hind limbs’ TSCIS was significantly higher in the HUC group than in ADM and PSC groups, p = 0.007. Both ADM and PSC groups exhibited loss of proprioception and mild to moderate ataxia compared to controls. MRI showed increased pathological findings in the PSC group when compared to the HUC group, p = 0.045. Histologically, the meningeal layer was thickened (inflammation) by 2–3 fold in ADM and PSC groups when compared to HUC and CTL groups, p = 0.01. There was lower MPO positive cells in the HUC group than in the ADM group, p = 0.018. Posterior column astrocyte activation was increased in ADM and PSC lambs compared to HUC lambs, p = 0.03. Conclusion: The HUC as a skin patch for in utero spina bifida repair preserves spinal cord function by reducing underlying inflammation when compared to ADM.

Preliminary Results of a Reverse Thermal Gel Patch for Fetal Ovine Myelomeningocele Repair

BACKGROUND

Prenatal surgical closure of Myelomeningocele (MMC) is considered part of the current age armamentarium. Clinical data has demonstrated the need for innovative patches to maximize the benefits and decrease the risks of this approach. Our team has developed a minimally invasive reverse thermal gel (RTG) patch with cellular scaffolding properties. Here, we demonstrate the initial gross and microscopic histological effects of this RTG patch in the fetal ovine model of MMC.

MATERIALS AND METHODS

A fetal ovine MMC defect was created at 68-75 days gestation, RTG patch application or untreated at 100-103 days, and harvest at 135-140 days. The RTG was applied to the defect and secured in place with an overlay sealant. Defect areas underwent gross and microscopic analysis for inflammation and skin development. Brains were analyzed for hindbrain herniation and hydrocephalus.

RESULTS

The untreated fetus (n = 1) demonstrated an open defect lacking tissue coverage, evidence of spinal cord injury, increased caspase-3, Iba1 and GFAP in spinal cord tissues, and hindbrain herniation and ventricular dilation. RTG treated fetuses (n = 3) demonstrated defect healing with well-organized dermal and epidermal layers throughout the entire healed tissue area overlaying the defect with minimal inflammation, reduced caspase-3, Iba1 and GFAP in spinal cord tissues, and no hindbrain herniation or ventricular dilation.

CONCLUSION

An RTG patch applied to MMC defects in fetal sheep promoted skin coverage over the defect, was associated with minimal inflammation of the spinal cord tissues and prevented brain abnormalities. The present findings provide exciting results for future comprehensive radiological, functional, and mechanistic evaluation of the RTG.

Hindbrain Herniation and Banana and Lemon Sign After Open Fetal Myelomeningocele Repair - When Do These Signs Disappear and is Shunting Predictable?

PURPOSE

 The aim was to describe the sonographic follow-up of hindbrain herniation (HH), the banana and lemon sign after fetal myelomeningocele (fMMC) repair, and the time of disappearance of these signs after the intervention, and to investigate any predictive value for the necessity of shunting during the infant's first year of life. Additionally, the sonographic evolution of the transcerebellar diameter (TCD) before and after fetal intervention was assessed.

PATIENTS AND METHODS

 The first 50 patients that underwent fMMC repair at Zurich Center for Fetal Diagnosis and Therapy (www.swissfetus.ch) were included in this study. Sonographic scans performed weekly after fMMC repair focusing on HH and banana and lemon signs were analyzed and compared between the shunted and the non-shunted group. ROC curves were generated for the time intervals of resolution of the signs in order to show their predictive accuracy for the need for shunting until 1 year of age.

RESULTS

 HH resolved in 48 fetuses (96 %) before delivery. The sonographic disappearance of HH within the first two weeks after fMMC repair was associated with a significantly lower incidence of shunt placement (OR 0.19; 95 % CI 0.4-0.9) during the first year of life (p = 0.03). All fetuses with persistent HH before delivery received a shunt. TCD growth was observed in all fetuses.

CONCLUSION

 The reversibility of HH within two weeks after fMMC repair is associated with an 80 % lower incidence of shunt placement during the infant's first year of life. Moreover, it allows the cerebellum to grow and to normalize its configuration.

Fetal and perinatal expression profiles of proinflammatory cytokines in the neuroplacodes of rats with myelomeningoceles: A contribution to the understanding of secondary spinal cord injury in open spinal dysraphism

The cellular and molecular mechanisms that presumably underlie the progressive functional decline of the myelomeningocele (MMC) placode are not well understood. We previously identified key players in posttraumatic spinal cord injury cascades in human MMC tissues obtained during postnatal repair. In this study we conducted experiments to further investigate these mediators in the prenatal time course under standardized conditions in a retinoic-acid-induced MMC rat model. A retinoic acid MMC model was established using time-dated Sprague-Dawley rats, which were gavage-fed with all-trans retinoic acid (RA; 60 mg/kg) dissolved in olive oil at E10. Control animals received olive oil only. Fetuses from both groups were obtained at E16, E18, E22. The spinal cords (SCs) of both groups were formalin-fixed or snap-frozen. Tissues were screened by real-time RT-PCR for the expression of cytokines and chemokines known to play a role in the lesion cascades of the central nervous system after trauma. MMC placodes exhibited inflammatory cells and glial activation in the later gestational stages. At the mRNA level, IL-1b, TNFa, and TNF-R1 exhibited significant induction at E22. IL1-R1 mRNA was induced significantly at E16 and E22. Double labeling experiments confirmed the costaining of these cytokines and their receptors with Iba1 (i.e., inflammatory cells), Vimentin, and Nestin in different anatomical SC areas and NeuN in ventral horn neurons. CXCL12 mRNA was elevated in control and MMC animals at E16 compared to E18 and E22. CX3CL1 mRNA was lower in MMC tissues than in control tissues on E16. The presented findings contribute to the concept that pathophysiological mechanisms, such as cytokine induction in the neuroplacode, in addition to the "first hit", promote secondary spinal cord injury with functional loss in the late fetal time course. Furthermore, these mediators should be taken into consideration in the development of new therapeutic approaches for open spinal dysraphism.

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.

Impact of Brain Malformations on Neurodevelopmental Outcome in Children with a History of Prenatal Surgery for Open Spina Bifida

INTRODUCTION

This retrospective study investigates brain malformations and their impact on neurodevelopmental outcome in children after prenatal surgery for spina bifida (SB).

METHODS

Sixty-one patients were included. On neonatal MRI, SB-associated brain malformations were assessed. Ventricular size, ventriculo-peritoneal shunt (VPS), and endoscopic third ventriculostomy (ETV) were also documented. Neurodevelopment was assessed with the Bayley-III and correlated with brain malformations, ventricular size, and VPS/ETV placement.

RESULTS

Chiari II malformation was detected in all patients. Corpus callosum (CC) abnormality was noted in 40%, heterotopies in 35%, and cerebellar parenchymal defects in 11%. 96% had ventriculomegaly; in 46%, VPS/ETV was performed. Cognitive and language testing yielded results in the low-average range (Bayley-III: Cognitive Composite Score 93.6, Language Composite Score 89.7), motor testing was below average (Motor Composite Score 77.4). CC abnormalities, heterotopies, and cerebellar defects were not associated with poorer Bayley-III scores, whereas patients with severe ventriculomegaly performed poorer in all subtests, significantly so for the language composite score. Patients requiring intervention for hydrocephalus had significantly lower scores in motor testing.

DISCUSSION/CONCLUSION

Additional brain malformations in open SB do not seem to have an impact on cognitive function at 2 years of age. Severe ventriculomegaly is a risk factor for poorer cognitive outcome; hydrocephalus surgery adds an additional risk for delayed motor function.

Longitudinal evaluation of motor function in patients who underwent prenatal or postnatal neural tube defect repair

OBJECTIVE

To compare the evolution of motor function from mid-gestation to 12 months of age between prenatally and postnatally repaired cases of open neural tube defect (ONTD).

METHODS

This was a retrospective cohort study of all fetuses that underwent prenatal (fetoscopic or open hysterotomy) or postnatal ONTD repair at a single institution between November 2011 and December 2018. The anatomical level of the lesion was defined as the upper bony spinal defect at initial magnetic resonance imaging assessment. Prenatal motor function of the lower extremities was evaluated by ultrasound according to the metameric level of the neurological lesion, based on the methodology of Carreras et al. Fetal motor function was assessed at referral, at 6 weeks after surgery in prenatally repaired cases or 6 weeks after referral in postnatally repaired cases (6-week follow-up) and at the last scan before delivery. In addition, motor function was assessed by a detailed neurological examination at birth and 12 months of age. First sacral (S1) neurological level of the lesion was considered as intact motor function. For statistical comparisons, we attributed numerical scores to each neurological level and motor function was expressed as median (range) neurological level. Motor function (as numerical score) and the proportion of cases with intact motor function and with motor function two or more levels better than expected based on the anatomical level of the lesion were compared between the prenatal- and postnatal-repair groups. Fetal motor function was compared to the anatomical level of the lesion at referral and a better motor function was defined when it was two or more levels better than the anatomical level of the lesion. To assess the evolution of motor function, we compared motor function at referral with that at each follow-up assessment using paired t-tests.

RESULTS

We included 127 patients with ONTD, of whom 93 underwent prenatal (51 fetoscopic and 42 open hysterotomy) and 34 postnatal repair. At the time of referral, cases in the prenatal- and postnatal-repair groups presented with a similar anatomical level of lesion (L3 (T9-S1) vs L3 (T7-S1); P = 0.52), similar motor function (S1 (L1-S1) vs S1 (L1-S1); P = 0.52) and a similar proportion of cases with intact motor function (81% vs 79%; P = 0.88) and with motor function two or more levels better than expected based on the anatomical level of the lesion (62% vs 74%; P = 0.24). When compared with prenatally repaired cases, postnatally repaired cases showed worse motor function at birth (S1 (L1-S1) vs L4 (L1-S1); P < 0.01) and at 12 months of age (S1 (L1-S1) vs L4 (L1-S1); P < 0.01). In the prenatal-repair group, motor function remained stable from the time of referral to 12 months of age (P = 0.26). Furthermore, the proportion of patients with intact motor function at referral (81% (75/93)) was similar to that at the 6-week follow-up (74% (64/87)), at the last scan before birth (74% (42/57)), at birth (68% (63/93)) and at 12 months of age (67% (39/58)) in the prenatal-repair group. In the postnatal-repair group, worse motor function, starting from the third trimester to 12 months of age, was observed. The proportion of patients with intact motor function at referral (79% (27/34)) was similar to that at 6-week follow-up (80% (12/15); P = 0.92), but was lower at the last assessment before birth (25% (2/8); P < 0.01), at birth (24% (8/34); P < 0.01) and at 12 months of age (28% (7/25); P < 0.01). Similar findings were noted when assessing the evolution of the proportion of cases with motor function two or more levels better than expected based on the anatomical level of the lesion in each group.

CONCLUSIONS

Infants with ONTD that underwent postnatal repair had worse motor function at birth and at 12 months of age than at mid-gestation and when compared with infants that underwent prenatal ONTD repair. Prenatal motor function assessment by ultrasound is an adequate tool to identify those infants who should have a good clinical motor function after delivery. Information obtained by fetal motor function assessment can have an important role for patient counseling and case selection for surgery. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Impact of the cystic neural tube defects on fetal motor function in prenatal myelomeningocele repairs: A retrospective cohort study

OBJECTIVE

To determine the impact of the lesion type (cystic [myelomeningocele] or flat [myeloschisis]) on the fetal motor function (MF) in cases candidates for prenatal open neural tube defect (ONTD) repair.

METHODS

Retrospective cohort study of patients with ONTD who underwent prenatal repair at a single institution between 2011 and 2019. The lesion type and the measurements of the length and width of the lesions to calculate the surface of the ellipsoid lesion were performed using MR scans. Prenatal MF of the lower extremities was evaluated by ultrasound following a metameric distribution at the time of referral. Intact MF was defined as the observation of plantar flexion of the ankle. Logistic regression was performed to determine the predictive value of the type of lesion for having an intact MF at the time of referral.

RESULTS

103 patients were included at 22.9 (19-25.4) weeks; 65% had cystic and 35% had flat lesions. At the time of referral, there was a higher proportion of cases with an intact MF in the presence of flat lesions (34/36; 94.4%) as compared to cystic lesion (48/67; 71.6%, p < 0.01). When adjusting for gestational age and anatomical level of the lesion, flat ONTD were 3.1 times more likely to be associated by intact motor function (CI%95 [2.1-4.6], p < 0.01) at the time of referral.

CONCLUSION

Cystic ONTD are more likely to be associated with impaired MF at mid-gestation in candidates for prenatal ONTD repair.

Emerging magnetic resonance imaging techniques in open spina bifida in utero

Magnetic resonance imaging (MRI) has become an essential diagnostic modality for congenital disorders of the central nervous system. Recent advancements have transformed foetal MRI into a clinically feasible tool, and in an effort to find predictors of clinical outcomes in spinal dysraphism, foetal MRI began to unveil its potential. The purpose of our review is to introduce MRI techniques to experts with diverse backgrounds, who are involved in the management of spina bifida. We introduce advanced foetal MRI postprocessing potentially improving the diagnostic work-up. Importantly, we discuss how postprocessing can lead to a more efficient utilisation of foetal or neonatal MRI data to depict relevant anatomical characteristics. We provide a critical perspective on how structural, diffusion and metabolic MRI are utilised in an endeavour to shed light on the correlates of impaired development. We found that the literature is consistent about the value of MRI in providing morphological cues about hydrocephalus development, hindbrain herniation or outcomes related to shunting and motor functioning. MRI techniques, such as foetal diffusion MRI or diffusion tractography, are still far from clinical use; however, postnatal studies using these methods revealed findings that may reflect early neural correlates of upstream neuronal damage in spinal dysraphism.

A Novel Model of Fetal Spinal Cord Exposure Allowing for Long-Term Postnatal Survival

BACKGROUND

The inherent morbidity associated with fetal ovine models of myelomeningocele (MMC) has created challenges for long-term survival of lambs. We aimed to develop a fetal ovine surgical spinal exposure model which could be used to evaluate long-term safety after direct spinal cord application of novel therapeutics for augmentation of in utero MMC repair.

METHODS

At gestational age (GA) 100-106, fetal lambs underwent surgical intervention. Laminectomy of L5-L6 was performed, dura was removed, and an experimental product was directly applied to the spinal cord. Paraspinal muscles and skin were closed and the fetus was returned to the uterus. Lambs were delivered via cesarean section at GA 140-142. Lambs were survived for 3 months with regular evaluation of motor function by the sheep locomotor rating scale. Spinal angulation was evaluated by magnetic resonance imaging at 2 weeks and 3 months.

RESULTS

Five fetal surgical intervention lambs and 6 control lambs who did not undergo surgical intervention were included. All lambs survived to the study endpoint of 3 months. No lambs had motor function abnormalities or increased spinal angulation.

CONCLUSION

This model allows for long-term survival after fetal spinal cord exposure with product application directly onto the spinal cord.

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 myelomeningocele repair at a university hospital: surgery and pregnancy outcomes

PURPOSE

Myelomeningocele (MMC) is an open neural tube defect that causes great morbidity. Prenatal open repair is the standard treatment; however, there are many complications related to the procedure. This study reports preliminary findings of open in utero repair of MMC in a public tertiary hospital in Brazil and describes factors that could be associated with increased surgical morbidity.

METHODS

Thirty-nine patients underwent open in utero repair of MMC from October 2015 to August 2019. The Clavien-Dindo classification of surgical complications and a classification system with the preterm definitions of the World Health Organization were used, respectively, for maternal and fetal complications.

RESULTS

A total of 28 mothers (71.8%) and 31 fetuses (79.5%) experienced at least one minor to major complication. Three mothers (7.7%) had a severe grade 4 complication. Fetal complications grades 3 to 5 occurred in 13 fetuses (33.3%). Gestational age at surgery and at birth were 24.88 ± 1.16 weeks and 33.23 ± 3.68 weeks, respectively. Preterm delivery occurred in 30 patients (76.9%), membrane rupture in 18 patients (46.2%) and chorioamnionitis in 13 patients (33.3%).

CONCLUSION

Open fetal surgery for MMC was performed at a Brazilian public tertiary care center, resulting in three grade 4 maternal complications. Relevant fetal complications were also present. The use of a standard classification system for complications renders studies more comparable and data more useful for counseling patients. Adjustments of perioperative procedures and long-term follow-up are needed to determine the real benefit of open in utero repair of MMC at our hospital.

Fetal surgery

Fetal medicine is a super-specialty enterprise and a technology-driven field. The growth and interest in fetal surgery can be largely attributed to advances in fetal imaging and bespoke instruments for in utero intervention. Previously fatal fetal conditions are now being treated using open surgery, minimally invasive procedures, and percutaneous fetal technologies. Several fetal conditions, including myelomeningocele and twin-to-twin transfusion syndrome, have been tested rigorously in RCTs. However, as the specialty of fetal surgery grows, a robust evidence base with long-term follow-up is obligatory for every procedure. This article offers an overview of fetal surgery and antenatal intervention. As more cutting edge therapies come into clinical practice, growing public opinion and medical ethics will play a significant role in the future of this multidisciplinary specialty.

Postoperative Ultrasound as a Predictor of Newborn Function and Ambulation after Open Fetal Myelomeningocele Repair

OBJECTIVE

Function of the lower extremities after prenatal myelomeningocele (MMC) repair is best assessed with ambulatory function at 30-36 months of age, but parents often ask about function before this milestone. Lower extremity movement can be assessed by ultrasound (US) and at the newborn exam (NE), but correlation between US, NE, and ambulation is not firmly established.

METHODS

This was a retrospective correlation study of fetuses that underwent open prenatal MMC repair at SSM Cardinal Glennon Fetal Care Institute, St. Louis, MO, between January 2011 and June 2017. Movement at the ankles, knees, and hips was assessed by US after open repair on postoperative days (PODs) 0-5 and at 32 weeks gestation. NE was performed by physical therapy or neurosurgery within the first month of life, and pediatric follow-up between 30 and 36 months of age was obtained to document ambulation.

RESULTS

Forty-two fetuses were included. Joint movement seen on US varied by POD: it was present on POD 1 in 7% of fetuses and 62% by POD 5. Degree of ventriculomegaly, lesion level, and lesion length did not have a significant effect on US, NE, or ambulation. Knee movement on POD 3 correlated with knee movement at NE (k = 0.58, p < 0.01), but only later knee movement correlated with ambulation (k = 0.28-0.46, p = 0.01). Hip movement at 32 weeks was the only single joint assessment that correlated with NE and ambulation (k = 0.45 and 0.46, p = 0.03 and 0.01, respectively).

CONCLUSION

Lower extremity movement increases between POD 1 and POD 5 in fetuses after open fetal MMC repair. Knee and hip movement on US at 32 weeks correlates with ambulation at 30-36 months. These data may inform counseling, and direct therapy and spark prospective investigations.

Prenatal and Postnatal Imaging Findings After Fetal Repair of Spinal Dysraphisms Using Cryopreserved Human Umbilical Cord Patch: A Case Series of 4 Patients

We describe a case series of imaging findings of 4 patients who underwent spinal dysraphisms repair in utero with novel patch material, cryopreserved human umbilical cord, in our institution. In our study, the prenatal and postnatal magnetic resonance imaging and ultrasound are reviewed and showed cord tethering and syrinx progression in all cases. Our report is the first description of magnetic resonance imaging and ultrasound findings in the context of using this novel patch in severe cases of spinal dysraphisms.

Alternative Hysterotomy Technique for the Reduction of Prenatal Complications of Intrauterine Myelomeningocele Repair

INTRODUCTION

The main aim of the fetal surgery of myelomeningocele (MMC) is the improvement in prognosis for children with this defect and at the same time high safety of the procedure for mother and fetus.

OBJECTIVE

The aim of the study was to determine the effectiveness of alternative hysterotomy technique for fetal surgery of MMC in prevention of essential perinatal complications.

METHODS

Forty-nine pregnant women diagnosed with fetal MMC (fMMC) who underwent classic hysterotomy without the use of stapler formed the study cohort. Two cases of intrauterine fetal death or neonatal death in the immediate perioperative period in the study group (SG) were excluded from further analyses. In the historical control group (46 patients) from our center hysterotomy was performed according to Management of Myelomeningocele Study (MOMS) protocol. The study cohort's outcomes were compared with the historical controls and with post-MOMS results in Children's Hospital of Philadelphia (CHOP) and Vanderbilt University Medical Center (VUMC).

RESULTS

In the SG we did not observe delivery before 30 weeks of gestation (0/47; 0%) and the incidence of chorionamniotic membrane separation (CMS, 3/47; 6%) and preterm premature rupture of membranes (PPROM, 7/47; 15%) was lower compared to the other groups. Preterm delivery as a result of uterine contractions occurred significantly less frequently in the SG (8/47; 17%). Fetal surgery with classic hysterotomy resulted in rare use of magnesium sulfate (3/47; 6%).

CONCLUSIONS

The alternative hysterotomy technique for fetal surgery of MMC results in low occurrences of CMS, PPROM, preterm delivery, and the rare use of tocolytics.

Neurosurgeons' opinions on the prenatal management of myelomeningocele

OBJECTIVE

Improvements in imaging and surgical technological innovations have led to the increasing implementation of fetal surgical techniques. Open fetal surgery has demonstrated more favorable clinical outcomes in children born with open myelomeningocele (MMC) than those following postnatal repair. However, primarily because of maternal risks but also because of fetal risks, fetal surgery for MMC remains controversial. Here, the authors evaluated the contemporary management of MMC in the hope of identifying barriers and facilitators for neurosurgeons in providing fetal surgery for MMC.

METHODS

An online survey was emailed to members of the Congress of Neurological Surgeons (CNS) and the International Society for Pediatric Neurosurgery (ISPN) in March 2019. The survey focused on 1) characteristics of the respondents, 2) the practice of counseling on and managing prenatally diagnosed MMC, and 3) barriers, facilitators, and expectations of fetal surgery for MMC. Reminders were sent to improve the response rate.

RESULTS

A total of 446 respondents filled out the survey, most (59.2%) of whom specialized in pediatric neurosurgery. The respondents repaired an average of 9.6 MMC defects per year, regardless of technique. Regardless of the departments in which respondents were employed, 91.0% provided postnatal repair of MMC, 13.0% open fetal repair, and 4.9% fetoscopic repair. According to the surgeons, the most important objections to performing open fetal surgery were a lack of cases available to become proficient in the technique (33.8%), the risk of maternal complications (23.6%), and concern for fetal complications (15.2%). The most important facilitators according to advocates of prenatal closure are a decreased rate of shunt dependency (37.8%), a decreased rate of hindbrain herniation (27.0%), and an improved rate of motor function (18.9%). Of the respondents, only 16.9% agreed that open fetal surgery should be the standard of care.

CONCLUSIONS

The survey results showed diversity in the management of patients with MMC. In addition, significant diversity remains regarding fetal surgery for MMC closure. Despite the apparent benefits of open fetal surgery in selected pregnancies, only a minority of centers and providers offer this technique. As a more technically demanding technique that requires multidisciplinary effort with less well-established long-term outcomes, fetoscopic surgery may face similar limited implementation, although the surgery may pose fewer maternal risks than open fetal surgery. Centralization of prenatal treatment to tertiary care referral centers, as well as the use of sophisticated training models, may help to augment the most commonly cited objection to the implementation of prenatal closure, which is the overall limited caseload.

Progressive hydrocephalus despite early complete reversal of hindbrain herniation after prenatal open myelomeningocele repair

OBJECTIVE

Open prenatal myelomeningocele (MMC) repair is typically associated with reversal of in utero hindbrain herniation (HBH) and has been posited to be associated with a reduction in both postoperative prenatal and immediate postnatal hydrocephalus (HCP) risks. However, the long-term postnatal risk of HCP following HBH reversal in these cases has not been well defined. The authors describe the results of a long-term HCP surveillance in a cohort of patients who underwent prenatal MMC repair at their institution.

METHODS

A retrospective review of all prenatal MMC repair operations performed at the Mayo Clinic between 2012 and 2017 was conducted. Pertinent data regarding the clinical courses of these patients before and after MMC repair were summarized. Outcomes of interest were occurrences of HBH and HCP and the need for intervention.

RESULTS

A total of 9 prenatal MMC repair cases were identified. There were 7 cases in which MRI clearly demonstrated prenatal HBH, and of these 86% (6/7) had evidence of HBH reversal after repair and prior to delivery. After a mean postnatal follow-up of 20 months, there were 3 cases of postnatal HCP requiring intervention. One case that failed to show complete HBH reversal after MMC repair required early ventriculoperitoneal shunting. The other 2 cases were of progressive, gradual-onset HCP despite complete prenatal HBH reversal, requiring endoscopic third ventriculostomy with choroid plexus cauterization at ages 5 and 7 months.

CONCLUSIONS

Although prenatal MMC repair can achieve HBH reversal in a majority of well-selected cases, the prevention of postnatal HCP requiring intervention appears not to be predicated on this outcome alone. In fact, it appears that in a subset of cases in which HBH reversal is achieved, patients can experience a progressive, gradual-onset HCP within the 1st year of life. These findings support continued rigorous postnatal surveillance of all prenatal MMC repair patients, irrespective of postoperative HBH outcome.

Minimally invasive fetal surgery for myelomeningocele: preliminary report from a single center

OBJECTIVE

Recent trials have shown the safety and benefits of fetoscopic treatment of myelomeningocele (MMC). The authors' aim was to report their preliminary results of prenatal fetoscopic treatment of MMC using a biocellulose patch, focusing on neurological outcomes, fetal and maternal complications, neonatal CSF leakage, postnatal hydrocephalus, and radiological outcomes.

METHODS

Preoperative assessment included clinical examination, ultrasound imaging, and MRI of the fetus. Patients underwent purely fetoscopic in utero MMC repair, followed by postoperative in utero and postnatal MRI. All participants received multidisciplinary follow-up.

RESULTS

Five pregnant women carrying fetuses affected by MMC signed informed consent for the fetoscopic treatment of the defect. The mean MMC size was 30.4 mm (range 19-49 mm). Defect locations were L1 (2 cases), L5 (2 cases), and L4 (1 case). Hindbrain herniation and ventriculomegaly were documented in all cases. The mean gestational age at surgery was 28.2 weeks (range 27.8-28.8 weeks). Fetoscopic repair was performed in all cases. The mean gestational age at delivery was 33.9 weeks (range 29.3-37.4 weeks). After surgery, reversal of hindbrain herniation was documented in all cases. Three newborns developed signs of hydrocephalus requiring CSF diversion. Neurological outcomes in terms of motor level were favorable in all cases, but a premature newborn died due to CSF infection and sepsis.

CONCLUSIONS

The authors' preliminary results suggest that fetoscopic treatment of MMC is feasible, reproducible, and safe for mothers and their babies. Neurological outcomes were favorable and similar to those in the available literature. As known, prematurity was the greatest complication.

Pediatric neurosurgeons' views regarding prenatal surgery for myelomeningocele and the management of hydrocephalus: a national survey

OBJECTIVE

The Management of Myelomeningocele Study (MOMS) compared prenatal with postnatal surgery for myelomeningocele (MMC). The present study sought to determine how MOMS influenced the clinical recommendations of pediatric neurosurgeons, how surgeons' risk tolerance affected their views, how their views compare to those of their colleagues in other specialties, and how their management of hydrocephalus compares to the guidelines used in the MOMS trial.

METHODS

A cross-sectional survey was sent to all 154 pediatric neurosurgeons in the American Society of Pediatric Neurosurgeons. The effect of surgeons' risk tolerance on opinions and counseling of prenatal closure was determined by using ordered logistic regression.

RESULTS

Compared to postnatal closure, 71% of responding pediatric neurosurgeons viewed prenatal closure as either "very favorable" or "somewhat favorable," and 51% reported being more likely to recommend prenatal surgery in light of MOMS. Compared to pediatric surgeons, neonatologists, and maternal-fetal medicine specialists, pediatric neurosurgeons viewed prenatal MMC repair less favorably (p < 0.001). Responders who believed the surgical risks were high were less likely to view prenatal surgery favorably and were also less likely to recommend prenatal surgery (p < 0.001). The management of hydrocephalus was variable, with 60% of responders using endoscopic third ventriculostomy in addition to ventriculoperitoneal shunts.

CONCLUSIONS

The majority of pediatric neurosurgeons have a favorable view of prenatal surgery for MMC following MOMS, although less so than in other specialties. The reported acceptability of surgical risks was strongly predictive of prenatal counseling. Variation in the management of hydrocephalus may impact outcomes following prenatal closure.

Urological Outcome after Fetal Spina Bifida Repair: Data from the Zurich Cohort

INTRODUCTION

Neurogenic lower urinary tract dysfunction (NLUTD) represents a severe burden for patients with open spina bifida (OSB). The effect of fetal OSB repair on the urological outcome remains unclear, as controversial data exist. The aim of this study was to further increment existing outcome data and to demonstrate that our earlier published positive preliminary results are not erratic.

METHODS

Data from standardized urological follow-up appointments of patients with fetal OSB repair operated at our center were analyzed. Data were obtained from urodynamic studies (UDSs) and radiologic exams performed in the newborn (gestational age 37-39 weeks), at ages of 6, 12, 18, and 24 months, and then at yearly intervals.

RESULTS

Of 82 patients (mean age 2.6 years, range 6 months to 7 years), 26 (32%) had a normal bladder function as demonstrated by UDSs. Of the 56 (68%) patients with NLUTD, 29 (51%) patients showed initially a normal UDS, but developed NLUTD in the follow-up, 19 (66%) of them spontaneously and another 10 (34%) in association with growth and development, or surgery of inclusion cysts. Radiologic abnormalities (upper tract dilatation and vesico-uretero-renal reflux) were seen in 15%, mainly patients with NLUTD.

CONCLUSION

Our results add an important set of information to the existing body of evidence. The data reconfirm our earlier published favorable preliminary results and support other studies that show a possible benefit of prenatal OSB repair on the urological outcome, but they also demonstrate that the positive effect remains limited.

Evaluation and Long-term Management of Neurogenic Bladder in Spinal Dysraphism

Spinal dysraphism, which includes conditions such as myelomeningocele and sacral agenesis, is one of the most common causes of congenital lower urinary tract dysfunction. Early evaluation of the neurogenic bladder serves to minimize renal damage, and the main goals of management include preserving renal function, achieving acceptable continence, and optimizing quality of life. The survival of patients with such conditions has improved to greater than 80% reaching adulthood, owing to advances in diagnostic and therapeutic modalities. The result is a real, and unfortunately often unmet, need for successful transitional care in this complex patient population. Clinicians must be able to identify the unique challenges encountered by patients with neurogenic bladder as they shift through different stages of their life.

Fetal spina bifida: What we tell the parents

Worldwide, about 150 000 infants are born with spina bifida yearly, making this condition one of the most common fetal central nervous system anomalies compatible with life. Over the last decade, major changes have been introduced in the prenatal diagnosis and management of spina bifida. In this review, we provide a brief summary of the current management of fetal spina bifida and present essential information that should be provided to expecting parents when their fetus has been diagnosed with spina bifida. This information is focused around common parental questions, as encountered in our typical clinical practice, to facilitate knowledge translation.

Hydrogel and neural progenitor cell delivery supports organotypic fetal spinal cord development in an ex vivo model of prenatal spina bifida repair

Studying how the fetal spinal cord regenerates in an ex vivo model of spina bifida repair may provide insights into the development of new tissue engineering treatment strategies to better optimize neurologic function in affected patients. Here, we developed hydrogel surgical patches designed for prenatal repair of myelomeningocele defects and demonstrated viability of both human and rat neural progenitor donor cells within this three-dimensional scaffold microenvironment. We then established an organotypic slice culture model using transverse lumbar spinal cord slices harvested from retinoic acid–exposed fetal rats to study the effect of fibrin hydrogel patches ex vivo. Based on histology, immunohistochemistry, gene expression, and enzyme-linked immunoabsorbent assays, these experiments demonstrate the biocompatibility of fibrin hydrogel patches on the fetal spinal cord and suggest this organotypic slice culture system as a useful platform for evaluating mechanisms of damage and repair in children with neural tube defects.

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.

Impact of the size of the lesion in prenatal neural tube defect repair on imaging, neurosurgical and motor outcomes: a retrospective cohort study

OBJECTIVES

(1) To compare brain findings between large and non-large neural tube defect (NTD); (2) to evaluate the impact of large lesion on the surgical parameters; (3) to study any associations between the size of the lesions and brain findings 6 weeks postoperatively and neurological short-term outcomes.

DESIGN

Retrospective cohort study.

SETTING

Texas Children's Hospital, between 2011 and 2018.

POPULATION

Patients who underwent prenatal NTD repair.

METHODS

Large lesion was defined when the lesion's surface was >75th centile of our cohorts' lesions.

MAIN OUTCOME MEASURES

Time of referral: ventriculomegaly and anatomical level of the lesion; surgery: duration and need for relaxing incisions. 6 weeks postoperative: hindbrain herniation (HBH) and ventriculomegaly. After delivery: dehiscence, need for hydrocephalus treatment and motor function.

RESULTS

A total of 99 patients were included, 25 of whom presented with large lesions. Type of lesion and ventriculomegaly were comparable between individuals with large and non-large lesions. Individuals with large lesions were associated with increased need for relaxing incisions by 5.4 times (95% CI 1.3-23.2, P = 0.02). Six weeks postoperatively, having a large lesion decreased by ten times the likelihood of having a postoperative reversal of HBH (odds ratio = 0.1, 95% CI 0.1-0.4, P < 0.01). At birth, larger lesions increased the risk for repair dehiscence by 6.1 times (95% CI 1.6-22.5, P < 0.01) and the risk of dehiscence or leakage of cerebrospinal fluid at birth by 5.5 times (95% CI 1.6-18.9, P < 0.01).

CONCLUSION

Prenatal repair of patients with large NTD presents a lower proportion of HBH reversal 6 weeks after the surgery, a higher risk of dehiscence and a higher need for postnatal repair.

TWEETABLE ABSTRACT

Evaluation of the size of fetal NTD can predict adverse neurological outcomes after prenatal NTD repair.

Fetal surgical intervention for myelomeningocele: lessons learned, outcomes, and future implications

Fetal myelomeningocele (fMMC) closure (spina bifida aperta) has become a care option for patients that meet inclusion criteria, but it is clear that fetal intervention, while improving outcomes, is not a cure. This review will: (1) focus on the rationale for fMMC surgery based on preclinical studies and observations that laid the foundation for human pilot studies and a randomized controlled trial; (2) summarize important clinical outcomes; (3) discuss the feasibility, efficacy, and safety of recent developments in fetal surgical techniques and approaches; and (4) highlight future research directions. Given the increased risk of maternal and fetal morbidity associated with prenatal intervention, accompanied by the increasing number of centres performing interventions worldwide, teams involved in the care of these patients need to proceed with caution to maintain technical expertise, competency, and patient safety. Ongoing assessment of durability of the benefits of fMMC surgery, as well as additional refinement of patient selection criteria and counselling, is needed to further improve outcomes and reduce the risks to the mother and fetus. WHAT THIS PAPER ADDS: High-quality prospective studies are needed to broaden the indication for fetal surgery in the general myelomeningocele population. Innovative minimally invasive approaches have had promising results, yet lack comprehensive and robust experimental or clinical evaluation. Important information to help families make informed decisions regarding fetal surgery for myelomeningocele is provided.

Suture techniques and patch materials using an in-vitro model for watertight closure of in-utero spina bifida repair

PURPOSE

Despite proven benefits of in-utero spina bifida (SB) repair, ≥30% of children at birth have Chiari II malformation or cerebrospinal fluid (CSF) leakage from the repair site. Our study's purpose was to determine CSF pressures in the myelomeningocele sac during mid-gestation in order to design an in-vitro model for evaluating different surgical methods used for watertight closure during in-utero SB repair.

METHODS

CSF pressures were measured during in-utero SB repair at mid-gestation. An in-vitro chicken thigh model, simulating fetal tissue, tested watertight closure when attached to the base of a water column. Primary closure methods were evaluated using defect sizes of 20 × 3 mm for minimal traction or 20 × 8 mm for moderate traction. Additionally, 3 common in-utero repair patches were compared using 15 × 15 mm defects.

RESULTS

Using 6-12.5 cm pre-determined CSF pressures, 165 in-vitro experiments were performed. Regardless of methodology we found that in 66 primary-based closures that minimal versus moderate wound edge traction provided better seals. The locking method was superior to the non-locking technique for watertight closure in 99 patch-based closures.

CONCLUSIONS

Minimal wound edge traction was best for primary closures, and locking sutures ideal for patch-based closures, however surgical techniques should be individualized to improve upon clinical outcomes.

Improved Coverage of Mouse Myelomeningocele With a Mussel Inspired Reverse Thermal Gel

BACKGROUND

Myelomeningocele (MMC) is an open neural tube defect of the spinal column. Our laboratory previously introduced a reverse thermal gel (RTG) as the first in situ forming patch for in utero MMC application. To overcome the challenges of anchoring the RTG in the wet amniotic environment to improve MMC coverage, we modified the RTG to mimic the underwater adhesive properties of mussels. We have separated this study into three separate hypotheses-based components: CONCLUSIONS: The DRTG demonstrates increased elasticity, cellular scaffolding properties, and improved MMC coverage in the Grhl3 mouse model. Future studies will be translated to the preclinical ovine model to evaluate this novel gel.

Heritable spina bifida in sheep: A potential model for fetal repair of myelomeningocele

BACKGROUND/PURPOSE

In 2004, a heritable occurrence of spina bifida was reported in sheep on a farm in the United States. We maintained and characterized the spina bifida phenotype in this flock to assess its potential as an alternative surgical model.

METHODS

A breeding strategy was developed in which the sheep were crossed to maintain or increase the occurrence of spina bifida. Measurements and observations were recorded regarding lesion size, birthweight, ambulatory capacity, or urological function, and necropsies were performed on spina bifida afflicted lambs in conjunction with magnetic resonance imaging to determine the character of the spina bifida defects and assess the presence of Chiari-like malformations or hydrocephalus.

RESULTS

The defects were observed to be more prevalent in ram lambs, and the rate of spina bifida per litter could be increased through backcrossing or by selection of a productive ewe breed. The lambs displayed a range of ambulatory and urological deficits which could be used to evaluate new fetal repair methodologies. Finally, affected lambs were shown to demonstrate severe Chiari malformations and hydrocephalus.

CONCLUSIONS

We have determined that use of these sheep as a natural source for spina bifida fetuses is feasible and could supplement the deficits of current sheep models for myelomeningocele repair.

LEVEL OF EVIDENCE

Level IV.

A Decade of Experience with the Ovine Model of Myelomeningocele: Risk Factors for Fetal Loss

INTRODUCTION

The ovine model is the gold standard large animal model of myelomeningocele (MMC); however, it has a high rate of fetal loss. We reviewed our experience with the model to determine risk factors for fetal loss.

METHODS

We performed a retrospective review from 2009 to 2018 to identify operative factors associated with fetal loss (early fetal demise, abortion, or stillbirth). Operative risk factors included gestational age at operation, operative time, reduction of multiple gestations, amount of replaced amniotic fluid, ambient temperature, and method of delivery.

RESULTS

MMC defects were created in 232 lambs with an overall survival rate of 43%. Of the 128 fetuses that died, 53 (42%) had demise prior to repair, 61 (48%) aborted, and 14 (11%) were stillborn. Selective reduction of multiple gestations in the same uterine horn was associated with increased fetal demise (OR 3.03 [95% CI 1.29-7.05], p = 0.01). Later gestational age at MMC repair and Cesarean delivery were associated with decreased abortion/stillbirth (OR 0.90 [95% CI 0.83-0.90], p = 0.03, and OR 0.37 [95% CI 0.16-0.31], p = 0.02), respectively.

CONCLUSION

Avoiding selective reduction, repairing MMC later in gestation, and performing Cesarean delivery decreases the rate of fetal loss in the ovine MMC model.

Prenatal Repair of Myelomeningocele and School-age Functional Outcomes

BACKGROUND AND OBJECTIVES

The Management of Myelomeningocele Study (MOMS), a randomized trial of prenatal versus postnatal repair for myelomeningocele, found that prenatal surgery resulted in reduced hindbrain herniation and need for shunt diversion at 12 months of age and better motor function at 30 months. In this study, we compared adaptive behavior and other outcomes at school age (5.9-10.3 years) between prenatal versus postnatal surgery groups.

METHODS

Follow-up cohort study of 161 children enrolled in MOMS. Assessments included neuropsychological and physical evaluations. Children were evaluated at a MOMS center or at a home visit by trained blinded examiners.

RESULTS

The Vineland composite score was not different between surgery groups (89.0 ± 9.6 in the prenatal group versus 87.5 ± 12.0 in the postnatal group; P = .35). Children in the prenatal group walked without orthotics or assistive devices more often (29% vs 11%; P = .06), had higher mean percentage scores on the Functional Rehabilitation Evaluation of Sensori-Neurologic Outcomes (92 ± 9 vs 85 ± 18; P < .001), lower rates of hindbrain herniation (60% vs 87%; P < .001), had fewer shunts placed for hydrocephalus (49% vs 85%; P < .001) and, among those with shunts, fewer shunt revisions (47% vs 70%; P = .02) than those in the postnatal group. Parents of children repaired prenatally reported higher mean quality of life z scores (0.15 ± 0.67 vs 0.11 ± 0.73; P = .008) and lower mean family impact scores (32.5 ± 7.8 vs 37.0 ± 8.9; P = .002).

CONCLUSIONS

There was no significant difference between surgery groups in overall adaptive behavior. Long-term benefits of prenatal surgery included improved mobility and independent functioning and fewer surgeries for shunt placement and revision, with no strong evidence of improved cognitive functioning.