Effects of birth advancement in Chiari malformation in a surgical myelomeningocele model in rabbits.

ABSTRACT

BACKGROUND/PURPOSE: In myelomeningocele (MMC), Chiari II malformation progresses during gestation because of the continuous loss of cerebrospinal fluid at the site of the defect. Our purpose was to assess the impact of birth advancement (BA) and prenatal corticosteroid treatment (PCT) on Chiari malformation in a surgical MMC model in rabbits. METHODS: A surgical MMC-like defect was created in 75 fetal rabbits. Animals were distributed into 4 groups depending on the treatment received not treated and those undergoing BA + PCT, BA, or PCT. The degree of Chiari malformation in newborn rabbits was defined as the percentage of downward protrusion of the hindbrain between the end of the occipital bone and the beginning of the first vertebral arch. RESULTS: The degree of hindbrain herniation was 80% (8.15) in the not treated group, 36.8% (10.57) in BA + PCT, 41.8% (8.27) in BA, and 44.4% (8.32) in PCT. The BA + PCT, BA, and PCT groups showed less severe hindbrain herniation than not treated animals (mean decrease, 39.86%; SD, 10.57; P = .000). There were no significant differences between the BA + PCT, BA, and PCT groups (P = .311). CONCLUSIONS: Birth advancement and prenatal administration of corticosteroids decrease the severity of the hindbrain herniation component of Chiari II malformation in surgical MMC in fetal rabbits.