MRI analysis of neurodevelopmental anatomy in myelomeningocele: prenatal vs postnatal repair.

OBJECTIVE: Prenatal myelomeningocele (MMC) repair offers improved motor function and decreased rates of cerebrospinal fluid (CSF) diversion compared to than postnatal repair. However, comparative analysis of other associated neuroanatomical findings is lacking. The purpose of this study is to use magnetic resonance imaging (MRI) imaging to compare characteristic Chiari II malformation stigmata in patients who underwent fetal MMC repair vs. postnatal repair.

METHODS: A retrospective review was performed of neonates who underwent prenatal or postnatal MMC repair at our institution and had postnatal MRIs. We analyzed anatomical findings characteristically seen with Chiari II malformation on brain MRI in patients who underwent prenatal MMC repair vs. postnatal repair.

RESULTS: CSF diversion was required in 24% of prenatal cohort vs. 67% of postnatal cohort (p = 0.002), and syrinx was present in 12% of prenatal cohort compared to 42% in postnatal cohort (p = 0.03). Corpus callosum (CC) morphology was abnormal in 52% of prenatal cohort vs. 53% of postnatal cohort (p = 0.92), while falx morphology was normal in 92% of the prenatal cohort vs. 34% of the postnatal cohort (p = <0.001). Prenatal cohort patients had shorter tentorium to foramen magnum distance than postnatal cohort patients (18.4mm vs. 22.4mm, p = 0.01), overall larger foramen magnum diameter (22.9mm vs. 18.9mm, p < 0.001), and a smaller mean degree of hindbrain herniation (1.5mm vs. 8.7mm, p < 0.001). Finally, the cerebral aqueduct was patent in 79% of prenatal cohort vs. 100% of postnatal cohort (p = 0.007). There was no significant difference in presence of gray matter heterotopia, presence of septum pellucidum, or size of massa intermedia between the two cohorts.

CONCLUSIONS: We report baseline variations in developmental neuroanatomy in patients with MMC including rates of CC dysgenesis, gray matter heterotopia and additional cranial and spinal MRI findings. We found that prenatal surgery results in changes to infratentorial anatomy, with minimal effect on supratentorial brain development. This information will be useful in myelomeningocele counseling and in understanding how prenatal repair of myelomeningocele affects brain development. This article is protected by copyright. All rights reserved.