BIRTH ADVANCEMENT DIMINISHES CHIARI MALFORMATION IN SURGICAL MIELOMENINGOCELE MODEL IN RABBITS

Abstract

The continuous leakage of cerebrospinal fluid in the mielomeningocele (MMC) area produces the Chiari II malformation. The aim of our study was to assess the effect of preterm delivery and prenatal corticosteroids administration in the degree of Chiari malformation.

Seventy-five out of 148 foetuses from 17 pregnant New Zealand White rabbits underwent lumbar three-level laminectomy and wide opening of dura-mater (surgical MMC). Animals were distributed in five groups: group T, foetuses with MMC, delivery at term and no other treatment; group TC, foetuses with MMC, delivery at term and prenatal administration of corticosteroids; group P, foetuses with MMC, delivery preterm and no other treatment; group PC, foetuses with MMC, delivery preterm and prenatal administration of corticosteroids; group C, controls. The degree of herniation was measured in percentage of decrease of the cerebellum between the inferior limit of the skull and the superior limit of the first vertebra, and compared among groups.

We obtained 7T, 5TC, 10P, 6PC, and 28C alive newborns. All groups with prenatal delivery or prenatal corticosteroids showed statistically significant minor degree of herniation than T-group: group TC IC 95% between 25.7 and 47.2% minor (p=0.000), group P IC 95% between 30.4 and 47.7% minor (p=0.000), group PC IC 95% between 32.6 and 55.4 minor (p=0.000). There were no statistically significant differences among groups TC and P (p=0,577), TC and PC (p=0,227) or P and PC (p=0,311).

Preterm delivery and prenatal administration of corticosteroids, together or separately, result in lower degree of Chiari malformation in a model of surgical MMC in rabbit fetuses.