First 60 fetal in-utero myelomeningocele repairs at Saint Louis Fetal Care Institute in the post-MOMS trial era: hydrocephalus treatment outcomes (endoscopic third ventriculostomy versus ventriculo-peritoneal shunt).

INTRODUCTION: The published results of the Management of Myelomeningocele Study (MOMS) trial in 2011 showed improved outcomes (reduced need for shunting, decreased incidence of Chiari II malformation, and improved scores of mental development and motor function) in the fetal prenatal repair group compared to the postnatal group. Historically, endoscopic third ventriculostomy (ETV) remains as a controversial hydrocephalus treatment option with high failure rates in pediatric patients with a history of myelomeningocele (MMC). We report hydrocephalus treatment outcomes in the fetal in-utero myelomeningocele repair patients who underwent repair at our Saint Louis Fetal Care Institute following the MOMS trial. We looked carefully at ETV outcomes in this patient population and we identified risk factors for failure.
METHODS: At our Saint Louis Fetal Care Institute, we followed the maternal and fetal inclusion and exclusion criteria used by the MOMS trial. The records of our first 60 fetal MMC repairs performed at our institute between 2011 and 2017 were examined. We retrospectively reviewed the charts, prenatal fetal magnetic resonance imaging (MRI) and ultrasound (US) imaging findings, postnatal brain MRI, and Bayley neurodevelopment testing results for infants and children who underwent surgical treatment of symptomatic hydrocephalus (VP shunt versus ETV). Multiple variables possibly related to ETV failure were considered for identifying risk factors for ETV failure.
RESULTS: Between May 2011 and March 2017, 60 pregnant female patients underwent the prenatal MMC repair for their fetuses between 20 and 26 weeks' gestational age (GA) utilizing the standard hysterotomy for exposure of the fetus, and microsurgical repair of the MMC defect. All MMC defects underwent successful in-utero repair, with subsequent progression of the pregnancy. At the time of this study, 58 babies have been born, 56 are alive since there were 2 mortalities in the neonatal period due to prematurity. One patient was excluded given lack of consent for research purposes. From the remaining 55 patient included in this study, a total of 30 infants and toddlers underwent treatment of hydrocephalus (ETV and VPS groups). Twenty-five patients underwent ETV (24 primary ETV and 1 after shunt failure). Nineteen patients underwent shunt placements (6 primary/13 after ETV failure). Mean GA at time of MMC repair for the ETV group was 24 + 6/7 weeks (range 22 + 4/7 to 25 + 6/7). Mean follow up for patients who had a successful ETV was 17.25 months (range 4-57 months). Bayley neurodevelopmental testing results were examined pre- and post-ETV. Overall ETV success rate was 11/24 (45.8%) at the time of this study. The total number of patients who underwent shunt placement was 19/55 (34.5%), while shunting rate was 40% in the MOMS trial. Using a simple logistic regression analysis to identify predictors of ETV failure, ETV age ≤6 months and gestational age ≥23 weeks at repair of myelomeningocele were significant predictors for ETV failure while in-utero ventricular stability ≤4 mm and in-utero ventricular size post-repair ≤15.5 mm were significant predictors for ETV success. None of the listed variables independently predicted classification into ETV success versus ETV failure groups when entered into multiple logistic regression analysis.
CONCLUSIONS: ETV, as an alternative to initial shunting, may continue to show promising results for treating fetal MMC repair patient population who present with symptomatic hydrocephalus during infancy and early childhood. Although our overall CSF diversion rate (ETV and VPS groups) in our fetal MMC group is higher than the MOMS trial, our shunting rate is lower given our higher incidence of patients with successful ETV. To our knowledge, this is the largest reported ETV series in patients who underwent fetal MMC repair. ETV deserves a closer look in the setting of improved hindbrain herniation in fetal in-utero MMC repair patients. In our series, young age (less than 6 months) and late GA at time of fetal MMC repair (after 23 weeks GA) were predictors for ETV failure, while in-utero stability of ventricular size (less than 4 mm) and in-utero ventricular size post-repair ≤15.5 mm were predictors for ETV success. Larger series and potential prospective randomized studies are required for further evaluation of risk factors for ETV failure in the fetal MMC patient population.