Detailed analysis of hydrocephalus patterns and associated variables in patients after open fetal repair and postnatal myelomeningocele/myeloschisis closure.

Background: Myelomeningocele (MMC) and myeloschisis (MS) are severe neural tube defects that result in neurodevelopmental impairments and hydrocephalus due to prenatal spinal cord exposure to amniotic fluid. Fetal MMC/MS (fMMC/MS) repair has become the standard of care in appropriately selected patients, demonstrating improved outcomes, including a reduction in the need for cerebrospinal fluid (CSF) diversion compared to postnatal MMC/MS (pMMC/MS) closure. This study is a detailed analysis of the incidence, timing, and imaging predictors of hydrocephalus and CSF diversion dependence in fetal repair and postnatal closure patients in the post-MOMS trial era.

Methods: A retrospective review was conducted of MMC/MS patients treated at a single institution between 2016 and 2023. Inclusion criteria required complete prenatal and postnatal follow-up data. Imaging metrics, including prenatal atrial diameter (AD) and postnatal fronto-occipital horn ratio (FOR), were analyzed alongside head circumference (HC) growth trajectories. Statistical analyses, including Youden's index, were performed to identify predictive cutoffs for shunt dependence.

Results: Among 333 MMC/MS patients, fetal repair significantly reduced permanent CSF diversion rates compared to postnatal closure (27.8% vs. 70.1%, p < 0.01). Timing of clinical hydrocephalus onset was delayed in fetal patients (24.2 weeks vs. 2.8 weeks, p < 0.01). HC of fetal patients was highly correlated with timing of shunt dependence. AD ≥ 10 mm and postnatal FOR ≥ 0.5 were associated with higher shunt dependence (p < 0.01). Optimal cut points for predicting shunt dependence were identified by Youden's index as 14 mm for AD and 0.57 for early postnatal FOR.

Conclusion: Fetal repair of MMC/MS decreases the incidence of clinical hydrocephalus and delays its onset compared to postnatal closure. Early imaging metrics (AD and FOR) may stratify hydrocephalus risk, enabling improved prenatal counseling and postnatal care. Long-term follow-up remains crucial for early detection and management of hydrocephalus in fetal MMC/MS patients.