Objective: To examine the impact of fetal myelomeningocele (MMC) repair on fetal head biometry and cerebrospinal fluid (CSF) spaces assessed by magnetic resonance imaging (MR) studies.
Study design: Axial measurements of intracranial structures were taken at defined anatomical landmarks. Pre- and postnatal head biometry data and CSF spaces obtained from in utero repaired MMC fetuses (n = 22) were compared to the pre- and postnatal measurements of MMC patients that underwent standard neurosurgical MMC repair after birth (n = 16) and a cohort of age-matched control patients (prenatal, n = 52; postnatal, n = 9).
Results: In fetuses with MMC, initial MR scans showed an almost complete absence of supratentorial and posterior fossa CSF spaces. No differences in postnatal CSF spaces were found between controls and prenatally repaired MMC newborns. In fetuses with postnatal MMC repair, CSF spaces remained significantly reduced (p < 0.0001). The mean ventricular diameter (VD) increase in the postnatal repaired MMC group was significantly higher compared to the mean percentage of VD increase in the fetal repaired MMC group (6.4 vs. 4.2 mm; p = 0.02). Pre- and postnatal brain thickness measurements were significantly reduced in both MMC populations compared to age-matched normal values (p < 0.0001). In contrast to postnatally repaired patients, in utero repair fetuses showed significant reversal of hindbrain herniation and normalization of the posterior fossa CSF spaces.
Conclusion: Mid-gestational repair of MMC promotes normalization of extra-axial CSF spaces. Due to progressive ventriculomegaly, brain thickness remains decreased in both prenatal repaired and age-matched non-repaired MMC patients when compared to age-matched normal values. Restoration of CSF volume in the posterior fossa after in utero repair is indicative of reversal of hindbrain herniation.