Limits of the surgically induced model of myelomeningocele in the fetal sheep

Abstract

Creation of a MMC-like lesion with an additional myelotomy does not always lead to hindbrain herniation. Our study suggests that CM should be assessed by ultrasound examination at the time of the prenatal repair to demonstrate the effectiveness of new techniques for the prenatal repair of MMC.

Safety and efficacy of fetal surgery techniques to close a spina bifida defect in the fetal lamb model: A systematic review

“…Firstly, high selection bias was mainly caused by an inadequate SB induction (Table , item 2; Table ). Actually, in those studies where the skin defect was <4 × 4 cm, the spontaneous closure rate among SB lambs with unclosed lesions was 17% to 80% instead of 0% when the skin defect was ≥4 × 4 cm (Figure ; Table ) . Animals that also had a myelotomy at the induction of SB were apparently less likely to have spontaneous closure (17%–56%) as opposed to those who did not have a myelotomy (22%–80%).…”

“…Animals that also had a myelotomy at the induction of SB were apparently less likely to have spontaneous closure (17%–56%) as opposed to those who did not have a myelotomy (22%–80%). Furthermore, with a defect <4 × 4 cm and additional myelotomy, the HH rate at birth was lower (22%–50%) than larger lesions with myelotomy (≥85%) . Another study with high selection bias, due to a < 21‐day interval between induction and repair, was excluded from the comparison as it had high attrition and reporting bias and was underpowered (Table ) .…”

“…Another study with high selection bias, due to a < 21‐day interval between induction and repair, was excluded from the comparison as it had high attrition and reporting bias and was underpowered (Table ) . This 3‐week interval is necessary to obtain a ≥ 85% rate of HH (instead of ≤50% after 2 weeks) when a myelotomy is performed at SB induction (Figure C‐D) …”

“…Assuming the clinical condition typically includes CSF leakage and HH at birth, this is best experimentally reproduced by creating a large enough defect associated with a myelotomy, ie, a posterior mid‐sagittal incision of the spinal canal. For instance, skin defects <4 × 4 cm at induction have a tendency to close spontaneously in 17% to 80% of the lambs . This is associated with an absence of HH at birth in 0% to 78% of cases .…”

Two-Port Fetoscopic Repair of Myelomeningocele in Fetal Lambs

“…A MMC lumbar defect was created at 75 days in 14 fetal lambs, as previously described [11, 12]. Briefly, low para-mammary incision and hysterotomy were performed to expose the fetal back.…”