Ventriculomegaly contraindicating fetal surgery in myelomeningocele

Fetuses with enlarged ventricles may be less likely than their counterparts to benefit from surgery in the womb to treat spina bifida, according to a study published in the Journal of Neurosurgery: Pediatrics.

Researchers found that fetuses with enlarged ventricles were more likely to require a second surgery to relieve a life-threatening build-up of pressure within the brain. Given the risks that fetal surgery poses for mother and newborn, the findings indicate that, in these cases, it may be better to wait until after birth to perform the corrective spinal surgery.

In 2011, the Management of Myelomeningocele (MOMS) study showed that surgically correcting the spinal defect while the fetus is in the womb greatly reduces the need to divert fluid away from the ventricles to relieve hydrocephalus.

In the current analysis of data from the original MOMS study, Noel B. Tulipan, MD, Vanderbilt University Medical Center, Nashville, Tennessee, and colleagues found that fetuses who had larger ventricles were equally as likely to require placement of a shunt during the first year after birth, regardless of when they underwent the spinal repair surgery.

“These results indicate that physicians should proceed with caution before recommending in utero surgery for a fetus with enlarged ventricles,” said Rosemary Higgins, MD, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), part of the National Institutes of Health (NIH), Bethesda, Maryland.

The original MOMS study found that infants who had undergone the surgery before birth were more likely to walk without crutches or other devices. At 30 months of age, the fetal surgery group also had higher scores in tests of mental and motor development. However, as with any surgery, the procedure presented risks. Babies who underwent surgery in the uterus were more likely to be born preterm than were those who had the surgery after birth. In addition, mothers in the fetal surgery group were at risk for having the surgical scar on the uterus tear or rupture during subsequent pregnancies.

“A major rationale for performing the surgery is to avoid having to place a shunt later on,” explained Dr. Higgins. “If it’s likely that a second surgery will be needed anyway, then it doesn’t appear that the potential benefits of an initial fetal surgery outweigh the risks.”

For the current analysis, researchers tabulated the results in a single, composite outcome, to highlight the differences between treatment and control groups. The primary combined outcome for this analysis was whether a child had died, had a shunt placed in the first year after birth, or met the study’s criteria for when to place a shunt.

Dr. Higgins explained that when the researchers began the original study, there were no formal recommendations for shunt placement, so the researchers developed a set of objective criteria to guide the treatment of patients in the study.

Of the women who took part in the study, 91 were randomised to the prenatal surgery group and 92 to the postnatal group. Of these, 72.5% in the prenatal surgery group and 97.8% in the postnatal surgery group met the criteria for inclusion in the primary outcome. Overall, 44% of children in the prenatal surgery group had a shunt placed, compared with 83.7% in the postnatal group.
When the women were first enrolled in the study, the researchers took magnetic resonance imaging scans of the fetuses’ brains. Irrespective of whether they were in the prenatal or postnatal surgery group, children with the largest ventricles were more likely to require a shunt than those with smaller ventricles.

For the prenatal surgery group, shunts were eventually placed in 20% of those with ventricles <10 mm, 45.2% with ventricles from 10 to <15 mm, and 79% with ventricle size ≥15 mm. For the postnatal surgery group, shunts were placed in 79.4%, 86%, and 87.5%, respectively.
The researchers concluded that fetuses with ventricles smaller than 10 mm are the ideal candidates for fetal surgery, while there appears to be no benefit, in relation to shunting, for fetuses with ventricles ≥15 mm. Cases in between should be evaluated carefully before deciding whether to refer them for fetal surgery, the authors concluded.

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Tulipan N, Wellons JC 3rd, Thom EA, Gupta N, Sutton LN, Burrows PK, Farmer D,
Walsh W, Johnson MP, Rand L, Tolivaisa S, D'alton ME, Adzick NS;  for the MOMS
Investigators. Prenatal surgery for myelomeningocele and the need for
cerebrospinal fluid shunt placement. J Neurosurg Pediatr. 2015 Sep 15:1-8. [Epub
ahead of print]

Abstract

OBJECT The Management of Myelomeningocele Study (MOMS) was a multicenter randomized trial comparing the safety and efficacy of prenatal and postnatal closure of myelomeningocele. The trial was stopped early because of the demonstrated efficacy of prenatal surgery, and outcomes on 158 of 183 pregnancies were reported. Here, the authors update the 1-year outcomes for the complete trial, analyze the primary and related outcomes, and evaluate whether specific prerandomization risk factors are associated with prenatal surgery benefit. METHODS The primary outcome was a composite of fetal loss or any of the following: infant death, CSF shunt placement, or meeting the prespecified criteria for shunt placement. Primary outcome, actual shunt placement, and shunt revision rates for prenatal versus postnatal repair were compared. The shunt criteria were reassessed to determine which were most concordant with practice, and a new composite outcome was created from the primary outcome by replacing the original criteria for CSF shunt placement with the revised criteria. The authors used logistic regression to estimate whether there were interactions between the type of surgery and known prenatal risk factors (lesion level, gestational age, degree of hindbrain herniation, and ventricle size) for shunt placement, and to determine which factors were associated with shunting among those infants who underwent prenatal surgery. RESULTS Ninety-one women were randomized to prenatal surgery and 92 to postnatal repair. The primary outcome occurred in 73% of infants in the prenatal surgery group and in 98% in the postnatal group (p < 0.0001). Actual rates of shunt placement were only 44% and 84% in the 2 groups, respectively (p < 0.0001). The authors revised the most commonly met criterion to require overt clinical signs of increased intracranial pressure, defined as split sutures, bulging fontanelle, or sunsetting eyes, in addition to increasing head circumference or hydrocephalus. Using these modified criteria, only 3 patients in each group met criteria but did not receive a shunt. For the revised composite outcome, there was a difference between the prenatal and postnatal surgery groups: 49.5% versus 87.0% (p < 0.0001). There was also a significant reduction in the number of children who had a shunt placed and then required a revision by 1 year of age in the prenatal group (15.4% vs 40.2%, relative risk 0.38 [95% CI 0.22-0.66]). In the prenatal surgery group, 20% of those with ventricle size < 10 mm at initial screening, 45.2% with ventricle size of 10 up to 15 mm, and 79.0% with ventricle size ≥ 15 mm received a shunt, whereas in the postnatal group, 79.4%, 86.0%, and 87.5%, respectively, received a shunt (p = 0.02). Lesion level and degree of hind-brain herniation appeared to have no effect on the eventual need for shunting (p = 0.19 and p = 0.13, respectively). Similar results were obtained for the revised outcome. CONCLUSIONS Larger ventricles at initial screening are associated with an increased need for shunting among those undergoing fetal surgery for myelomeningocele. During prenatal counseling, care should be exercised in recommending prenatal surgery when the ventricles are 15 mm or larger because prenatal surgery does not appear to improve outcome in this group. The revised criteria may be useful as guidelines for treating hydrocephalus in this group.