The effect of prenatal treatment with steroids and preterm delivery in a model of myelomeningocele on the rabbit foetus.

Damage of neural elements (spinal cord and encephalus) in myelomeningocele (MMC) seems to be progressive during gestation because of amniotic fluid chemical contact and continuous leakage of CSF. We studied the effect of preterm delivery and steroid treatment in a model of MMC in the rabbit foetus. Twelve New Zealand White rabbits underwent laparotomy and hysterotomy at 23 days of gestation. Fifty-nine out of 107 foetuses underwent lumbar laminectomy (three to four levels). Dura was opened to expose the neural elements to the amniotic fluid. Six rabbits underwent caesarean section on gestational day 31 for fetal harvest; three of them had no treatment (group T) and three received corticosteroid treatment (group TC). The other six rabbits underwent caesarean section on gestational day 29 for fetal harvest (preterm delivery); three of them had no treatment (group P) and three received corticosteroid treatment (group PC). Alive newborns were clinically, neurophysiologically and histologically analysed. None of mothers died during the procedure. After birth, animals in group preterm showed statistically significant less deformity than animals in group at term. Lower kyphosis was observed in group PC (preterm and steroids). Pain related and spontaneous mobility of lower extremities was higher in groups treated with corticosteroids (TC and PC). Only newborns at term (T and TC groups) showed response to evoked potentials (CMEPs). The response was earlier and higher in group treated with steroids (TC). Histologically, we observed progressive lesion of the spinal cord. Groups treated with steroids (TC and PC) show less inflammatory response. Arnold-Chiari malformation was present in all groups. Animals in group preterm with steroids show statistically significant less herniation than those group at term. Preterm delivery and prenatal steroid therapy seem to be an effective treatment to get less neural injury (spinal cord and encephalus) in myelomeningocele foetuses.