Comparison between two surgical technique for prenatal correction of meningomyelocele in sheep

INTRODUCTION: The incidence of neural tube defects is about 1/1000 births. In myelomeninocele, the intrauterine treatment with the classical neurosurgical technique suggest better neurological prognosis for the fetus, than postnatal treatment, but it is associated with maternal and fetal complications. New correction techniques are being studied to decrease maternal and fetal morbidity. OBJECTIVE: To compare the effects on the medulla of two surgical techniques for intrauterine correction of myelomeningocele-like defect in sheep. METHODS: In 15 pregnant sheep a myelomeningocele -like defect (laminectomy and dural excision) was created in the lumbar region in 90o day gestation. The type of correction was randomized. In group 1 the defect was corrected using the classic neurosurgical technique of three layers suture (dura-mater, muscle and skin closure) performed by a neurosurgeon. In group 2, a fetal medicine specialist used a biosynthetic cellulose patch to protect the medulla and only the skin was sutured above it. Near term (132o day gestation) fetuses were sacrificed for pathological analysis. RESULTS: One maternal death occurred, early preterm labour, and late preterm labour occurred in 3 and 4 cases, respectively. A total of 10 cases were available for pathological analysis, 6 in group 1 and 4 in group 2. In group 1, all the cases showed a adherence of the medulla to the scar (meningoneural adhesion) and a destruction of the normal architecture of nervous tissue, whithout view of posterior funiculus and in 5 of 6 cases without view of grey matter. In group 2, in all the cases were observed a formation of an organized tissue involving the cellulose patch, a neoduramater, separating the nervous tissue of adjacent muscle, preserving the posterior funicullus and grey matter. CONCLUSION: The simplified new technique was better than the classical neurosurgical technique. It preserved the nervous tissued and avoided the adherence of the medulla to the scar. This suggests the current technique used for the correction of spina bifida in humans may need to be reassessed