Spina Bifida

Posted by • March 16th, 2011

When photographs from some of the earliest in-utero surgeries for myelomeningocele appeared in the media in the late 1990s, they attracted attention. The images showed a second-trimester fetus’s hand extended from the mother’s abdominal incision. These surgeries closed the spina bifida birth defects known as myelomeningoceles, the most common form of open neural tube defects. Prior to these pioneering surgeries, the surgical closures were performed after birth. The damage to the spinal cord and brain, however, was often irreversible.

Now, a randomized controlled trial by Adzick et. al published in NEJM confirms that this prenatal surgery has benefits. The Management of Myelomeningocele Study (MOMS), which started in 2003 and was to conclude November 2013, was stopped for efficacy of prenatal surgery late last year after the recruitment of 183 of a planned 200 patients. Women were randomized to undergo either prenatal surgery before 26 weeks of gestation or standard postnatal repair. Results were based on 158 patients whose children were evaluated at 12 months and 30 months. Authors, in a unique arrangement, received agreements from all other U.S. fetal intervention centers that they would not perform myelomeningocele surgery while the trial was ongoing at the Children’s Hospital of Philadelphia, Vanderbilt University, and the University of California, San Francisco.

One primary outcome was a composite of fetal or neonatal death or the need for placement of a cerebrospinal fluid shunt by the child’s first birthday; the other primary outcome, at 30 months, was a composite of mental development and motor function.

The first primary outcome occurred in 68% of the infants in the prenatal-surgery group and in 98% of those in the postnatal-surgery group. Rates of shunt placement were 40% in the prenatal-surgery group and 82% in the postnatal-surgery group. Prenatal surgery also resulted in improvement in the composite score for mental development and motor function at 30 months. It is fair to note that although there was improvement in this composite score, that was entirely the result of the improved motor function with no improvement in mental development despite the observed reduced need for shunting at 12 months.

While prenatal surgery was an improvement, it wasn’t a panacea. “Not all infants benefited from the early intervention,” the authors write in their discussion, “and some had a poor neuromotor outcome.” This group also had higher rates of spontaneous membrane rupture (46% in the prenatal-surgery group vs. 8% in the postnatal-surgery group), oligohydramnios (21% vs. 4%), preterm birth (79% vs. 15%), and more complications associated with prematurity.

In an accompanying editorial, Dr. Joe Leigh Simpson and Dr. Michael Greene write that results from the study are “a major step in the right direction,” but “caution is necessary.” Because all the cases were managed by the same three study centers, they “should have developed near-optimal prowess.” Now that the data from this study are published, other centers will start their own programs, “diluting experience and necessitating individual center-specific learning curves. Fetal results may not be as good as those in MOMS, and maternal complications could be increased.”

Also, most women who showed interest in the trial were ineligible or declined to participate, the editorialists observed, and there was only 15% participation of those screened.

The editorialists ultimately advise pragmatic counsel to mothers who need to make what is inarguably an emotionally-charged decision: “Our job as physicians is to communicate options and available data to patients as lucidly as possible while assiduously adhering to the principles of nondirective genetic counseling.

For many women, the 20% absolute improvement in ambulation at the age of 3 years and the decreased need for shunting may be perceived as sufficient to justify the increased risk of maternal complications, but it should be recognized that outcomes after prenatal surgery were less than perfect in MOMS.”

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