Prenatal evolution of hindbrain herniation following fetal open neural tube defect repair

Prenatal open neural tube defect (ONTD) repair improves motor function and reduces hydrocephalus treatment by ensuring watertight closure of the defect. Hindbrain herniation (HBH) reversal is often observed postoperatively, but its association with postnatal outcomes remains unclear.

To assess HBH evolution via fetal MRI following prenatal ONTD repair, and its association with reduced hydrocephalus treatment and absence of cerebrospinal fluid (CSF) leak.

This retrospective study included fetuses who underwent prenatal ONTD repair via laparotomy-assisted fetoscopic or open-hysterotomy techniques. Preoperative and 6-week postoperative fetal MRIs were reviewed by two blinded experts using a modified Sutton classification. HBH reversal was categorized as complete (cerebellum above the foramen magnum), partial (improved but still below the foramen magnum), or absent (no change). Associations with hydrocephalus treatment and CSF leak were analyzed using logistic regression, adjusting for potential confounders. A P-value <0.05 was considered statistically significant.

One hundred forty-six fetuses (fetoscopic, 112; open-hysterotomy, 34) were included. The median gestational age at repair was 25.1 weeks (range, 21.3-26.4). At 6 weeks, 103/146 (70.5%) achieved complete HBH reversal, 17/146 (11.6%) had partial reversal, and 26/146 (17.8%) showed no reversal. CSF leak was significantly lower in complete HBH reversal (3/103 (2.9%)) compared to the partial/no reversal group (14/43 (32.6%), P<0.01), with a 12.33-fold increased risk (95% CI (2.55-45.31), P<0.01) for CSF leak in the latter group. Hydrocephalus treatment was lower in complete HBH reversal (18/86 (20.9%)) versus partial/no reversal (25/36 (69.4%), P<0.01), with a 5.58-fold increased risk (95% CI (2.98-24.74), P<0.01).

Complete HBH reversal occurred in 70.5% after prenatal ONTD repair and was associated with lower risks of CSF leak and hydrocephalus. Fetal MRI at 6 weeks post-surgery is a reliable prognostic indicator for assessing repair integrity and hydrocephalus risk.