Severe and progressive neuronal loss in myelomeningocele begins before 16 weeks of pregnancy

Molecular insights into myelomeningocele via proteomic analysis of amniotic fluid

Despite numerous studies on fetal therapy for myelomeningoceles (MMC), the pathophysiology of this malformation remains poorly understood. This study aimed to analyze the biochemical profile and proteome of amniotic fluid (AF) supernatants from MMC fetuses to explore the prenatal pathophysiology. Biochemical analysis of 61 AF samples from MMC fetuses was compared with 45 healthy fetuses' samples. Proteome analysis was conducted in 18 MMC and 18 healthy singleton fetuses, and in 5 dichorionic pregnancies with MMC fetuses and their healthy co-twins. ELISA tests were used to validate proteome results. Biochemical analysis revealed anal incontinence in 37 % of MMC cases, absent in controls (p < 0.0001). Proteomics identified 2453 quantified proteins with 39 significantly up-regulated and 10 down-regulated in the MMC group. Up-regulated proteins included ectodomains of CHL1, APLP1, SEZ6, SEZ6L, known targets of the protease BACE1. We explored the overlap of neonatal cerebrospinal fluid (CSF) and AF proteome and highlighted 411 proteins in common, mostly upregulated in MMC AF compared to controls. Our study thoroughly characterizes the AF proteome and reveals numerous proteins to be changed as a consequence of MMC. Many of these proteins are typical constituents of CSF. No difference in AF inflammation markers were observed between MMC and healthy fetuses. SIGNIFICANCE: This study provides good evidence that neuroepithelial destruction in MMC is independent of inflammation or presumed meconium toxicity.

Role of Amniotic Fluid Toxicity in the Pathophysiology of Myelomeningocele: A Narrative Literature Review

Myelomeningocele is a birth defect whose clinical manifestations are due both to incomplete neural tube closure and the progressive destruction of exposed neuroepithelium during pregnancy. Two hypotheses have been formulated to explain the spinal cord damage in utero: mechanical trauma and chemical factors. The objective of this review was to summarize the current insights about the potential role of amniotic fluid in spinal cord damage in myelomeningocele. Numerous histological and clinical data on animals and humans strongly suggest a progressive degeneration of neural tissue including loss of neural cells, astrogliosis, inflammation, and loss of normal architecture. However, few data have been published about the direct toxicity of amniotic fluid in this neural degeneration, including the potentially toxic effect of meconium. Finally, the chemical and cellular modifications of amniotic fluid composition in myelomeningocele could reflect both the process (toxic effect of meconium) and the consequences of neuroepithelium destruction (release of neural cells). Fetal surgery not only stops the leakage of the cerebrospinal fluid but also reduces the toxic effect of amniotic fluid by restoring the intrauterine environment. Identification of amniotic fluid neurotoxic factors could lead to the development of therapeutic agents designed to protect spinal tissue and improve fetal myelomeningocele outcomes.

Development of a double-layer electrospun patch as a potential prenatal treatment for myelomeningocele

Myelomeningocele (MMC) is a congenital defect of the spine characterised by meningeal and spinal cord protrusion through the open vertebral arches. This defect causes progressive prenatal damage of the spinal cord, leading to lifelong handicap. Although mid-trimester surgical repair may reduce part of the handicap, an earlier and less invasive approach would further improve the prognosis, possibly minimising maternal and foetal risks. Several studies have proposed an alternative approach to surgical repair by covering the defect with a patch and protecting the exposed neural tissue. Our study aims to elaborate on a waterproof and biodegradable bioactive patch for MMC prenatal foetal repair. We developed a double-layer patch that can provide a waterproof coverage for the spinal cord, with a bioactive side, conducive to cell proliferation, and an antiadhesive side to avoid its attachment to the medulla.

Prenatal predictors of need for cerebrospinal fluid diversion in infants following prenatal repair of open spina bifida; systematic review and meta-analysis

OBJECTIVE

This study aimed to investigate prenatal predictors of the need for cerebrospinal fluid diversion in infants following prenatal repair of open spina bifida.

DATA SOURCES

A systematic search was performed to identify relevant studies published from inception until June 2022 in the English language using the databases PubMed, Scopus, and Web of Science.

STUDY ELIGIBILITY CRITERIA

We included retrospective and prospective cohort studies and randomized controlled trials reporting on prenatal repair of open spina bifida.

METHODS

The random-effects model was used to pool the mean differences or odds ratios and the corresponding 95% confidence intervals. Heterogeneity was assessed using the I2 value.

RESULTS

A total of 9 studies including 948 pregnancies undergoing prenatal repair of open spina bifida were included in the final analysis. Prenatal factors that were significantly associated with the need for postnatal cerebrospinal fluid diversion were gestational age at surgery ≥25 weeks (odds ratio, 4.2; 95% confidence interval, 1.8-9.9; I2=54%; P=.001), myeloschisis (odds ratio, 2.2; 95% confidence interval, 1.1-4.1; I2=0.0%; P=.02), preoperative lateral ventricle width ≥15 mm (odds ratio, 4.5; 95% confidence interval, 2.9-6.9; I2=0.0%; P<.0001), predelivery lateral ventricle width (mm) (mean difference, 8.3; 95% confidence interval, 6.4-10.2; I2=0.0%; P<.0001), and preoperative lesion level at T12-L2 (odds ratio, 2.5; 95% confidence interval, 1.03-6.3; I2=68%; P=.04). Factors that significantly reduced the need for postnatal shunt placement were gestational age at surgery <25 weeks (odds ratio, 0.3; 95% confidence interval, 0.15-0.6; I2=67%; P=.001) and preoperative lateral ventricle width <15 mm (odds ratio, 0.3; 95% confidence interval, 0.2-0.4; I2=0.0%; P<.0001).

CONCLUSION

This study demonstrated that among fetuses that underwent surgical repair of open spina bifida, having gestational age at surgery of ≥25 weeks, preoperative lateral ventricle width of ≥15 mm, myeloschisis lesion type, and preoperative lesion level above L3 was predictive of the need for cerebrospinal fluid diversion during the first year of life.

Long-Term Imaging Follow-up from the Management of Myelomeningocele Study

BACKGROUND AND PURPOSE

Short-term results demonstrate that prenatal repair of a myelomeningocele is associated with a reduction in hydrocephalus and an increased likelihood of the reversal of Chiari II malformations compared with postnatal repair. The purpose of this study was to identify the long-term imaging findings at school age among subjects who underwent pre- versus postnatal repair of a myelomeningocele.

MATERIALS AND METHODS

A subset of subjects enrolled in the Management of Myelomeningocele Study who underwent either prenatal (n = 66) or postnatal (n = 63) repair of a lumbosacral myelomeningocele and had follow-up brain MR imaging at school age were included. The prevalence of posterior fossa features of Chiari II malformation and supratentorial abnormalities and the change in these findings from fetal to school-age MR imaging were compared between the 2 groups.

RESULTS

Prenatal repair of a myelomeningocele was associated with higher rates of normal location of fourth ventricle and lower rates of hindbrain herniation, cerebellar herniation, tectal beaking, brainstem distortion, and kinking at school age compared with postnatal repair (all P < .01). Supratentorial abnormalities, including corpus callosal abnormalities, gyral abnormalities, heterotopia, and hemorrhage, were not significantly different between the 2 groups (all P > .05). The rates of resolution of brainstem kinking, tectal beaking, cerebellar and hindbrain herniation, and normalization of fourth ventricle size from fetal to school age MR imaging were higher among the prenatal compared with postnatal surgery group (all, P < .02).

CONCLUSIONS

Prenatal repair of a myelomeningocele is associated with persistent improvement in posterior fossa imaging findings of Chiari II malformation at school age compared with postnatal repair.

Systematic classification and comparison of maternal and obstetrical complications following 2 different methods of fetal surgery for the repair of open neural tube defects

BACKGROUND

In utero repair of open neural tube defects using an open hysterotomy approach (hereafter referred to as "open") has been shown to reduce the need for ventriculoperitoneal shunting and to improve motor outcomes for affected infants. Laparotomy-assisted fetoscopic repair (hereafter referred to as "hybrid") is an alternative approach that may confer similar neurologic benefits while reducing the incidence of hysterotomy-related complications.

OBJECTIVE

This study aimed to analyze procedure-related maternal and fetal complications of in utero repair using the Clavien-Dindo classification, and to compare the outcomes of the hybrid and open approaches.

STUDY DESIGN

This was a retrospective cohort study conducted in a single center between September 2011 and July 2021. All patients who met the Management of Myelomeningocele Study criteria and who underwent either hybrid or open fetal surgery were included. Maternal complications were classified using a unique adaptation of the Clavien-Dindo scoring system, allowing the development of a comprehensive complication index score specific to fetal surgery. Primary fetal outcome was defined as gestational age at delivery and summarized according to the World Health Organization definitions of preterm delivery.

RESULTS

There were 146 fetuses with open neural tube defects who were eligible for, and underwent, in utero repair during the study period. Of these, 102 underwent hybrid fetoscopic repair and 44 underwent open hysterotomy repair. Gestational age at the time of surgery was higher in the hybrid group than in the open group (25.1 vs 24.8 weeks; P=.004). Maternal body mass index was lower in the hybrid than in the open group (25.4 vs 27.1 kg/m2; P=.02). The duration of hybrid fetoscopic surgery was significantly longer in the hybrid than in the open group (250 vs 164 minutes; P<.001). There was a significantly lower Clavien-Dindo Grade III complication rate (4.9% vs 43.2%; P<.001) and a significantly lower overall comprehensive maternal complication index (8.7 vs 22.6; P=.021) in the hybrid group than in the open group. Gestational age at delivery was significantly higher in the hybrid group than in the open group (38.1 vs 35.8 weeks; P<.001), and this finding persisted when gestational age at delivery was analyzed using the World Health Organization definitions of preterm delivery.

CONCLUSION

Use of our adaptation of the standardized Clavien-Dindo classification to assess the maternal complications associated with in utero open neural tube defect repair provides a new method for objectively assessing different fetal surgical approaches. It also provides a much-needed standardized tool to allow objective comparisons between methods, which can be used when counseling patients. The hybrid open neural tube defect repair was associated with lower rates of maternal adverse events , and later gestational age at delivery compared with the open approach.

Local host response of commercially available dural patches for fetal repair of spina bifida aperta in rabbit model

OBJECTIVE

Fetal surgery for spina bifida aperta (SBA) by open hysterotomy typically repairs anatomical native tissue in layers. Increasingly, fetoscopic repair is performed using a dural patch followed by skin closure. We studied the host response to selected commercially available patches currently being used in a fetal rabbit model for spina bifida repair.

METHODS

SBA was surgically induced at 23-24 days of gestation (term = 31 days). Fetal rabbits were assigned to unrepaired (SBA group), or immediate repair with Duragen™ or Durepair™. Non-operated littermates served as normal controls. At term, spinal cords underwent immunohistochemical staining including Nissl and glial fibrillary acidic protein. We hypothesized that spinal cord coverage with a dural patch and skin closure would preserve motor neuron density within the non-inferiority limit of 201.65 cells/mm² and reduce inflammation compared to unrepaired SBA fetuses.

RESULTS

Motor neuron density assessed by Nissl staining was conserved both by Duragen (n = 6, 89.5; 95% CI -158.3 to -20.6) and Durepair (n = 6, 37.0; 95% CI -132.6 to -58.5), whereas density of GFAP-positive cells to quantify inflammation was lower than in unrepaired SBA-fetuses (SBA 2366.0 ± 669.7 cells/mm² vs. Duragen 1274.0 ± 157.2 cells/mm² ; p = 0.0002, Durepair 1069.0 ± 270.7 cells/mm² ; p < 0.0001).

CONCLUSIONS

Covering the rabbit spinal cord with either Duragen or Durepair followed by skin closure preserves motor neuron density and reduces the inflammatory response.

Fetal MRI prior to intrauterine surgery of open neural tube defects: What does the radiologist need to know

The management of myelomeningocele study trial showed significant prognostic improvement in fetal repair before 26 weeks of gestation. Hence, surgery in utero represents the best treatment option for open-neural tube defects (NTDs). Fetal surgery of open-NTDs has specific inclusion and exclusion criteria, which can be adequately studied with fetal MRI. The main concern: the spine (spinal defects other than Myelomeningocele and Myeloschisis, the level of the lesion higher than T1 or lower than S1 and the degree of kyphosis ≥ 30°), the skull/brain (no cerebellum herniation and Chiari II malformation and the presence of any intracranial abnormality unrelated to open NTDs), the uterus (cervix length less than 2 cm, multiple gestations and placental and uterine abnormalities) and any other fetal abnormality not attributed to spinal defect. In this review, we describe the fundamental role of fetal MRI in supporting therapeutic decisions in pre-surgery intrauterine planning through the accurate and comprehensive description of findings, providing a proposal of a structured report. In addition, we describe how post-surgical MRI is important in investigating the effectiveness of surgery and detecting repairing complications.

Neuropathology Evaluation of in Utero Correction of Myelomeningocele and Complications of Late-Onset GBS Infection

Background: Myelomeningocele (MMC) causes significant morbidity and mortality. Efforts have been directed to correct this defect in utero. The neuropathology literature on antenatally repaired MMC and associated complications in humans is limited. Case report: A 12-day-old female, who underwent prenatal MMC repair via a two-layer closure (dural replacement patch, primary skin closure), was born at 34 weeks' gestation. Her group B streptococcus positive mother received appropriate antepartum prophylactic antibiotics. She remained stable until day 11 of life when she underwent rapid clinical deterioration. Despite aggressive intervention, she expired on day 12. Review of placental pathology showed maternal and fetal inflammatory response. Autopsy revealed Gram-positive cocci and inflammation within the basilar leptomeninges and lumbosacral region. Neural and dermal elements were present within the MMC repair. Conclusion: This case documents integration of the dermal matrix patch to neural elements, adhering the spinal cord to scar tissue, the clinical implications of which remain unclear.

Neurocognitive Effects of Fetal Exposure to Anesthesia

Surgery during pregnancy occurs when maternal or fetal needs outweigh the status quo, yet much uncertainty remains regarding the effects of anesthesia and surgery on fetal neurodevelopment. This article will review common maternal and fetal indications for invasive procedures, along with contemporary research on fetal neurodevelopment following anesthesia and surgery, focusing on future areas of investigation.

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.

Myelomeningocele Surgery over the 10 Years Following the MOMS Trial: A Systematic Review of Outcomes in Prenatal versus Postnatal Surgical Repair

Background and Objectives: Myelomeningocele is the most severe form of spina bifida, a congenital neural tube defect arising from an incomplete neural tube closure during early development with damage worsening with advancing gestational age. The Management of Myelomeningocele Study (MOMS) Trial proved that surgery performed before 26 weeks of gestation significantly improved the prognosis, significantly changing treatment paradigms. This article aims to provide a review of the changes and updates in spina bifida repair over the 10-year period following the MOMS Trial. Material and methods: We performed a systematic review in the PubMed and Cochrane databases as well as a hand-search of high-impact journals using the reference list of all identified articles, searching for randomized controlled trials and observational studies. Results: We identified 27 articles published between 2011 and 2021 that fulfilled the inclusion criteria and review them in the present study. Conclusions: With growing experience and with the improvement of prenatal open and fetoscopic techniques, the outcome of SB-associated conditions could be improved and the risks to both the mother and the fetus reduced. A continuous follow-up of the treated infants and further randomized trials are essential to study the complications and advantages or disadvantages of any given treatment strategy.

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

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

Screening for Open Spina Bifida in a Routine Clinical Setting at the First-Trimester Scan: A Prospective Multicentre Cohort Study

OBJECTIVE

The aim of this study was to investigate the performance of screening for open spina bifida (OSB) integrated into the routine first-trimester screening.

METHOD

This is a prospective multicentre study of 4,755 women undergoing first-trimester ultrasound scans over a 4-year period. Measurements of the brainstem (BS) diameter and brainstem-to-occipital-bone (BSOB) distance were performed. The cisterna magna (CM) was measured in the tilted axial view.

RESULTS

Pregnancy outcome data were available for 4,658 fetuses included in this study. There were 5 fetuses with OSB, and in all of them, the BS/BSOB ratio and the CM measurements were abnormal. The sensitivity and specificity of a BS/BSOB ratio >1 were 100%. The sensitivity of a CM width <5th centile was 100%, and the specificity was 95.1%. In 4.6% of cases, the BS/BSOB ratio was between the 95th percentile and 1. In 87.1% of these cases, the CM was normal, and 12.9% had a CM below the 5th percentile.

CONCLUSION

Screening for OSB is feasible in routine first-trimester scans. The BS/BSOB ratio shows a very good sensitivity and specificity. In cases with near-normal values for the BS/BSOB ratio, the CM width might be helpful for further assessment.

Preclinical stem cell therapy in fetuses with myelomeningocele: A systematic review and meta-analysis

OBJECTIVE

We performed a systematic review to summarize the efficacy and safety of in utero stem cells application in preclinical models with myelomeningocele (MMC).

METHODS

The study was registered with PROSPERO (CRD42019160399). We searched MEDLINE, Embase, Web of Science, Scopus and CENTRAL for publications articles on stem cell therapy in animal fetuses with MMC until May 2020. Publication quality was assessed by the SYRCLE's tool. Meta-analyses were pooled if studies were done in the same animal model providing similar type of stem cell used and outcome measurements. Narrative synthesis was performed for studies that could not be pooled.

RESULTS

Nineteen and seven studies were included in narrative and quantitative syntheses, respectively. Most used mesenchymal stem cells (MSCs) and primarily involved ovine and rodent models. Both intra-amniotic injection of allogeneic amniotic fluid (AF)-MSCs in rat MMC model and the application of human placental (P)-MSCs to the spinal cord during fetal surgery in MMC ovine model did not compromise fetal survival rates at term (rat model, relative risk [RR] 1.03, 95% CI 0.92-1.16; ovine model, RR 0.94, 95% CI 0.78-1.13). A single intra-amniotic injection of allogeneic AF-MSCs into rat MMC model was associated with a higher rate of complete defect coverage compared to saline injection (RR 16.35, 95% CI 3.27-81.79). The incorporation of human P-MSCs as a therapeutic adjunct to fetal surgery in the ovine MMC model significantly improved sheep locomotor rating scale after birth (mean difference 5.18, 95% CI 3.36-6.99).

CONCLUSIONS

Stem cell application during prenatal period in preclinical animal models is safe and effective.