Transactions of the Twentieth Annual Meeting of the Society For Maternal-Fetal Medicine—ContinuedHindbrain herniation develops in surgically created myelomeningocele but is absent after repair in fetal lambs☆
Section snippets
Material and methods
A surgical open-canal myelomeningocele-like spinal cord defect was created in fetal lambs at 75 days’ gestation (term, 147 days), modifying previously described techniques (Fig 1).6Briefly, the lumbar region of the fetus was exposed through a hysterotomy. An oval skin excision over the lumbar portion of the spine and excision of soft tissue and the paraspinal muscles were performed. Subsequently, a laminectomy (first through fourth lumbar vertebrae)
Results
A myelomeningocele was surgically created in 20 fetal lambs (Fig 2).Four fetuses died shortly after creation of the lesion. One fetus was found to have a spontaneous closure of the defect 3 weeks after creation of the lesion. Five fetal sheep underwent an Alloderm repair, 4 underwent primary surgical repair, and 6 had no repair. Unfortunately, because of a preexisting infection of several ewes with
Comment
Infants with myelomeningocele always have magnetic resonance imaging evidence of hindbrain herniation.9 In addition to this hindbrain herniation, other anomalies of the central nervous system, such as enlargement of the massa intermedia, the presence of polymicrogyria, and the absence of the corpus callosum comprising the Chiari II malformation, are seen.2 Ultrasonography reveals the characteristic shape of the calvarium and frontal bones, referred to as the lemon sign, and the dysplastic
Acknowledgements
We thank William Hoffman, MD, and Bruce Storrs, MD, for their invaluable expertise and help in the primary repair of fetal myelomeningocele.
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Reprint requests: Bettina W. Paek, MD, The Fetal Treatment Center, University of California at San Francisco, San Francisco, CA 94143-0570.