Limits of the surgically induced model of myelomeningocele in the fetal sheep.
OBJECTIVE
The prevention of Chiari type II malformation (CM) is commonly used as a primary outcome for the evaluation of techniques of fetal myelomeningocele (MMC) surgery in the fetal lamb. The aim of our study was to investigate the frequency of the associated CM in the MMC fetal sheep model and to investigate the contribution of prenatal ultrasound evaluation of CM at the time of prenatal repair.


METHODS
A MMC-like lesion was surgically created at 75 days of gestation in 21 fetuses performing a L1-L5 laminectomy followed by an excision of the exposed dura and a midline myelotomy. At a 90-day gestation, among the 19 alived fetuses, a conventional repair of the MMC-like lesion was performed in seven, four of whom underwent cerebral ultrasound (US) examination before the repair. Twelve fetuses remained untreated (control group). All fetuses underwent post-mortem examination (PM) at 138 days.


RESULTS
At a 90-day gestation, CM was demonstrated by US examination in all four evaluated fetuses. At birth, CM was found in 3/6 control whether CM was absent in all alived fetuses in the prenatal repair group (n = 4).


CONCLUSIONS
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.
Unité de Médecine Fœtale et d'Echographie, Pôle de Périnatalité, Hôpital Armand Trousseau, APHP, Paris 6, 26 Avenue A. Netter, 75012, Paris, France.
L
L
Guilbaud
C
C
Garabedian
F
F
Di Rocco
C
C
Fallet-Bianco
S
S
Friszer
M
M
Zerah
J M
JM
Jouannic
D000818:Animals; D001139:Arnold-Chiari Malformation / Q000209:etiology* / Q000601:surgery*; D004195:Disease Models, Animal; D004622:Embryo, Mammalian; D005333:Fetus / Q000473:pathology; D005865:Gestational Age; D007796:Laminectomy / Q000009:adverse effects*; D008591:Meningomyelocele / Q000150:complications / Q000601:surgery*; D008953:Models, Anatomic; D012756:Sheep; D014463:Ultrasonography