The significance of hindbrain herniation reversal following prenatal repair of neural tube defects.

Objective: The aim of this study was to determine whether reversal of hindbrain herniation (HBH) on MRI following prenatal repair of neural tube defects (NTDs) is associated with reduced rates of ventriculoperitoneal (VP) shunt placement or endoscopic third ventriculostomy (ETV) within the 1st year of life.

Methods: This is a secondary analysis of prospectively collected data from all patients who had prenatal open repair of a fetal NTD at a single tertiary care center between 2012 and 2020. Patients were offered surgery according to inclusion criteria from the Management of Myelomeningocele Study (MOMS). Patients were excluded if they were lost to follow-up, did not undergo postnatal MRI, or underwent postnatal MRI without a report assessing hindbrain status. Patients with HBH reversal were compared with those without HBH reversal. The primary outcome assessed was surgical CSF diversion (i.e., VP shunt or ETV) within the first 12 months of life. Secondary outcomes included CSF leakage, repair dehiscence, CSF diversion prior to discharge from the neonatal intensive care unit (NICU), and composite neonatal morbidity. Demographic, prenatal sonographic, and operative characteristics as well as outcomes were assessed using standard univariate statistical methods. Multivariate logistic regression models were fit to assess for independent contributions to the primary and secondary outcomes.

Results: Following exclusions, 78 patients were available for analysis. Of these patients, 38 (48.7%) had HBH reversal and 40 (51.3%) had persistent HBH on postnatal MRI. Baseline demographic and preoperative ultrasound characteristics were similar between groups. The primary outcome of CSF diversion within the 1st year of life was similar between the two groups (42.1% vs 57.5%, p = 0.17). All secondary outcomes were also similar between groups. Patients who had occurrence of the primary outcome had greater presurgical lateral ventricle width than those who did not (16.1 vs 12.1 mm, p = 0.02) when HBH was reversed, but not when HBH was persistent (12.5 vs 10.7 mm, p = 0.49). In multivariate analysis, presurgical lateral ventricle width was associated with increased rates of CSF diversion before 12 months of life (adjusted OR 1.18, 95% CI 1.03-1.35) and CSF diversion prior to NICU discharge (adjusted OR 1.18, 95% CI 1.02-1.37).

Conclusions: HBH reversal was not associated with decreased rates of CSF diversion in this cohort. Predictive accuracy of the anticipated benefits of prenatal NTD repair may not be augmented by the observation of HBH reversal on MRI.