Fetal Surgery for Myelomeningocele
Abstract & Commentary
Synopsis: Intrauterine repair of myelomeningocele reduces the incidence of hindbrain herniation and hydrocephaly necessitating VP shunt placement, but does increase the likelihood of premature delivery.
Source: Bruner JP, et al. JAMA 1999;282:1819-1825.
To determine if the intrauterine repair of myelomeningocele improves neonatal outcomes, Bruner and colleagues conducted a single-institution, nonrandomized, observational study between January 1990 and February 1999. This report describes the first 29 study patients compared with 23 controls matched for diagnosis and the level of the lesion. All infants were followed for at least six months after delivery. The procedure was performed on fetuses with no other malformations and a normal karyotype at a gestational age of 24-30 weeks. At surgery, an 8 cm incision was made in the uterine fundus, and the repair was performed in a manner similar to that used in the newborn. Patients received magnesium sulfate, indomethacin, and, subsequently, a terbutaline pump for tocolysis. Amniocentesis was done at 35-36 weeks to assess fetal lung maturity, and a cesarean delivery was performed as soon as the fetal lungs were mature. In control patients, the myelomeningocele was repaired within 48 hours of delivery.
The main outcome measures included the requirement for ventriculoperitoneal (VP) shunt placement after birth, gestational age at delivery, birthweight, and obstetrical complications. In utero repair significantly reduced the need for VP shunt placement in study infants (59% vs 91%), reduced hindbrain herniation (38% vs 95%), and, if a shunt was needed, delayed its insertion (50 days of age vs 5 days). In utero surgery resulted in a significantly higher rate of oligohydramnios (48% vs 4%) as well as a greater likelihood for hospitalization for preterm uterine contractions (50% vs 9%). Study patients were delivered significantly earlier (33.2 vs 37 weeks) and had a lower birthweight (2171 g vs 3075 g). All study infants survived.
Several significant complications occurred. In one patient with polyhydramnios, reduction of the amniotic fluid volume at surgery led to placental abruption and required delivery of an infant that did well. One mother required laparotomy for a small bowel obstruction five weeks after fetal surgery, while another patient was admitted at 33 weeks gestation with abdominal pain. An ultrasound demonstrated a fetal leg protruding through the uterine incision. The fetus was delivered, and both the infant and mother did well.
Bruner et al conclude that intrauterine repair of myelomeningocele reduces the incidence of hindbrain herniation and hydrocephaly necessitating VP shunt placement, but does increase the likelihood of premature delivery.
Comment by Steven G. Gabbe, MD
Myelomeningocele occurs in 4.5 per 10,000 live births. Most cases can be detected by midpregnancy with maternal serum alpha-fetoprotein screening and ultrasound. Until recently, only two options were available for patients whose fetus was found to have a myelomeningocele, pregnancy termination or expectant management and delivery, usually by cesarean section. Since 1990, Bruner et al at Vanderbilt University have been developing techniques to repair these defects in utero. They believe the early correction of this malformation improves outcome not only because the anatomic defect is closed, but because the cord is protected from continued exposure to amniotic fluid. The results are encouraging, although Bruner et al emphasize that the study infants must be followed closely to assess neurologic outcome including ambulation, bladder and bowel control, and developmental milestones. Similar findings were reported by Sutton and colleagues in the same issue of JAMA.1 This series from Children’s Hospital of Philadelphia included 10 patients undergoing a similar procedure at 22-25 weeks gestation. One infant was delivered prematurely at 25 weeks gestation and died. The remaining nine surviving neonates demonstrated improvement in hindbrain herniation on preoperative and postoperative MRI scans. Bruner et al emphasize that closure of the fetal defect stops the leaking of cerebrospinal fluid (CSF), establishes back pressure in the posterior fossa, and allows more normal circulation of CSF.
Both reports are exciting, but we must temper our enthusiasm while further experience is gained and critically important follow-up studies are done. Attention must also be paid to the adverse obstetrical outcomes, which include oligohygramnios, preterm labor and delivery, and uterine scar separation.
Which of the following infant outcomes are known to be improved by in utero surgery for fetal myelomeningocele?
a. Fecal continence
b. Ambulation
c. Intelligence quotient (IQ)
d. Requirement for VP shunting
e. Urinary continence
Reference
1. Sutton LN, et al. JAMA 1999;282:1826-1831.
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