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

Parental Management Choices and Discordant Ultrasound Findings in Referrals for Fetal Spina Bifida

OBJECTIVE

The severity of spina bifida aperta can be assessed prenatally by ultrasound. Morphological findings assist parents in choosing between management options. We aimed to document those management choices since the introduction of fetal surgery, and compare initial ultrasound findings prior to referral to findings in a fetal surgery center.

METHOD

Single center cohort study of 245 consecutive fetuses with a second-trimester diagnosis of SBA. Data included nature of referral (for assessment or for surgery), condition-specific findings on ultrasound, and further management. We compared the reported findings on the initial ultrasound to ours for the presence of hindbrain herniation, lesion level, ventricular width, kyphosis, leg movement, and club feet.

RESULTS

Seventy-two percent (n = 177) of fetuses met the eligibility criteria for surgery; in 60% (n = 106) parents opted for fetal surgery. Of 136 patients specifically referred for surgery, 27 were ineligible (20%). Of the others, 93 proceeded with surgery. In up to 28% (n = 30) of surgery referrals, eligibility criteria such as lesion level (n = 30, 28%) or leg movement (72%, n = 78) as severity indicators were not reported.

CONCLUSION

Fetal surgery uptake was high in patients referred for surgery. Second assessment in a fetal surgery center often reveals additional relevant information.

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.

Length of hysterotomy for fetal spina bifida repair is associated with prematurity risk

OBJECTIVE

To investigate whether prenatal repair of spina bifida aperta through mini-hysterotomy results in less prematurity, as compared to standard hysterotomy, when adjusting for known prematurity risks.

METHODS

We performed a bi-centric, propensity score matched, controlled study, that is, adjusting for factors earlier reported to result in premature delivery or membrane rupture, in consecutive women having prenatal repair either through stapled hysterotomy or sutured mini-hysterotomy (≤3.5 cm). Matches were pairwise compared and cox-regression analysis was performed to define the hazard ratio of delivery <37 weeks.

RESULTS

Of 346 meeting the MOMS-criteria, 78 comparable pairs were available for matched-controlled analysis. Mini-hysterotomy patients were younger and had a higher BMI. Mini-hysterotomy was associated with a 1.67-lower risk of delivery <37 weeks (hazard ratio: 0.60; 95% CI: 0.42-0.85; p = 0.004) and 1.72 for delivery <34 + 6 weeks (hazard ratio: 0.58; 95% CI: 0.34-0.97; p = 0.037). The rate of intact uterine scar at birth (mini-hysterotomy: 98.7% vs. hysterotomy: 90.4%; p = 0.070), the rate of reversal of hindbrain herniation within 1 week after surgery (88.9% vs. 97.4%; p = 0.180) and the rate of cerebrospinal fluid leakage (0% vs. 2.7%; p = 0.50) were comparable.

CONCLUSION

Prenatal spina bidifa repair through mini-hysterotomy was associated with a later gestational age at delivery and a comparable intact uterus rate without apparent compromise in neuroprotection.

High-fidelity, low-cost synthetic training model for fetoscopic spina bifida repair

BACKGROUND

Fetoscopic spina bifida repair is increasingly being practiced, but limited skill acquisition poses a barrier to widespread adoption. Extensive training in relevant models, including both ex vivo and in vivo models may help. To address this, a synthetic training model that is affordable, realistic, and that allows skill analysis would be useful.

OBJECTIVE

This study aimed to create a high-fidelity model for training in the essential neurosurgical steps of fetoscopic spina bifida repair using synthetic materials. In addition, we aimed to obtain a cheap and easily reproducible model.

STUDY DESIGN

We developed a 3-layered, silicon-based model that resemble the anatomic layers of a typical myelomeningocele lesion. It allows for filling of the cyst with fluid and conducting a water tightness test after repair. A compliant silicon ball mimics the uterine cavity and is fixed to a solid 3-dimensional printed base. The fetal back with the lesion (single-use) is placed inside the uterine ball, which is reusable and repairable to allow for practicing port insertion and fixation multiple times. Following cannula insertion, the uterus is insufflated and a clinical fetoscopic or robotic or prototype instruments can be used. Three skilled endoscopic surgeons each did 6 simulated fetoscopic repairs using the surgical steps of an open repair. The primary outcome was surgical success, which was determined by water tightness of the repair, operation time <180 minutes and an Objective Structured Assessment of Technical Skills score of ≥18 of 25. Skill retention was measured using a competence cumulative sum analysis of a composite binary outcome of surgical success. Secondary outcomes were cost and fabrication time of the model.

RESULTS

We made a model that can be used to simulate the neurosurgical steps of spina bifida repair, including anatomic details, port insertion, placode release and descent, undermining of skin and muscular layer, and endoscopic suturing. The model was made using reusable 3-dimensional printed molds and easily accessible materials. The 1-time startup cost was €211, and each single-use, simulated myelomeningocele lesion cost €9.5 in materials and 50 minutes of working time. Two skilled endoscopic surgeons performed 6 simulated, 3-port fetoscopic repairs, whereas a third used a Da Vinci surgical robot. Operation times decreased by more than 30% from the first to the last trial. Six experiments per surgeon did not show an obvious Objective Structured Assessment of Technical Skills score improvement. Competence cumulative sum analysis confirmed competency for each surgeon.

CONCLUSION

This high-fidelity, low-cost spina bifida model allows simulated dissection and closure of a myelomeningocele lesion. VIDEO ABSTRACT.

3D vs. 2D simulated fetoscopy for spina bifida repair: a quantitative motion analysis

3D imaging technology is becoming more prominent every day. However, more validation is needed to understand the actual benefit of 3D versus conventional 2D vision. This work quantitatively investigates whether experts benefit from 3D vision during minimally invasive fetoscopic spina bifida (fSB) repair. A superiority study was designed involving one expert team ([Formula: see text] procedures prior) who performed six 2D and six 3D fSB repair simulations in a high-fidelity animal training model, using 3-port access. The 6D motion of the instruments was recorded. Among the motion metrics are total path length, smoothness, maximum speed, the modified Spectral Arc Length (SPARC), and Log Dimensionless Jerk (LDLJ). The primary clinical outcome is operation time (power 90%, 5% significance) using Sealed Envelope Ltd. 2012. Secondary clinical outcomes are water tightness of the repair, CO[Formula: see text] insufflation volume, and OSATS score. Findings show that total path length and LDLJ are considerably different. Operation time during 3D vision was found to be significantly shorter compared to 2D vision ([Formula: see text] vs. [Formula: see text] min; p [Formula: see text] 0.026). These results suggest enhanced performance with 3D vision during interrupted suturing in fetoscopic SBA repair. To confirm these results, a larger-scale follow-up study involving multiple experts and novice surgeons is recommended.

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.

Patient empowerment improves follow-up data collection after fetal surgery for spina bifida: institutional audit

OBJECTIVES

To define and grade fetal and maternal adverse events following fetal surgery for spina bifida and to report on the impact of engaging patients in collecting follow-up data.

METHODS

This prospective single-center audit included 100 consecutive patients undergoing fetal surgery for spina bifida between January 2012 and December 2021. In our setting, patients return to their referring unit for further pregnancy care and delivery. On discharge, referring hospitals were requested to return outcome data. For this audit, we prompted patients and referring hospitals to provide data in cases of missing outcomes. Outcomes were categorized as missing, returned spontaneously or returned following additional request, by the patient and/or referring center. Postoperative maternal and fetal complications until delivery were defined and graded according to Maternal and Fetal Adverse Event Terminology (MFAET) and the Clavien-Dindo classification.

RESULTS

There were no maternal deaths, but severe maternal complications occurred in seven women (anemia in pregnancy, postpartum hemorrhage, pulmonary edema, lung atelectasis, urinary tract obstruction and placental abruption). No cases of uterine rupture were reported. Perinatal death occurred in 3% of fetuses and other severe fetal complications in 15% (perioperative fetal bradycardia/cardiac dysfunction, fistula-related oligohydramnios, chorioamnionitis and preterm prelabor rupture of membranes (PPROM) before 32 weeks). PPROM occurred in 42% of patients and, overall, delivery took place at a median gestational age of 35.3 weeks (interquartile range, 34.0-36.6 weeks). Information provided following additional request, from both centers and patients but mainly from the latter, reduced missing data by 21% for gestational age at delivery, 56% for uterine-scar status at birth and 67% for shunt insertion at 12 months. Compared with the generic Clavien-Dindo classification, the MFAET system ranked complications in a more clinically relevant way.

CONCLUSIONS

The nature and rate of severe complications following fetal surgery for spina bifida were similar to those reported in other large series. Spontaneous return of outcome data by referring centers was low, yet patient empowerment improved data collection. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

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.