Fetal Myelomeningocele Repair: Short-Term Clinical Outcomes
Abstract & Commentary
Synopsis: Early experience with fetal MMC repair suggests a decreased need for ventriculoperitoneal shunting, arrest, or slowing of progressive ventriculomegaly, and consistent resolution of hindbrain herniation. However, further long-term follow-up is needed to evaluate neurodevelopment and bladder and bowel function.
Source: Johnson MP, et al. Am J Obstet Gynecol. 2003;189:482-487.
The team at Children’s Hospital of Philadelphia has been involved in various in utero fetal surgical ventures. In the August issue of the American Journal of Obstetrics and Gynecology they have reported their experience with open repair of fetal neural tube defects. They selected for analysis 50 fetuses operated upon between 20 and 25 weeks who had defects that started at S1 or higher and had no ultrasound signs of lower limb dysfunction. These fetuses were compared with historical control fetuses with similar lesions who were not operated upon in utero.
They found that all the repaired fetuses had reversal of their hindbrain herniation, and, as an indirect result, only 48% required ventriculo-peritoneal shunts after birth, compared with 85% of historical controls. They also found that in 57% of cases the infants had better motor function than would be predicted by the anatomic level of the defect—this was not compared against historical controls.
Comment by John C. Hobbins, MD
Recently I had a patient, referred for an ultrasound evaluation because of an elevated MSAFP, who said, "I want you to look for any cause for this elevation other than a spinal defect. This I am not worried about because I know it can be fixed." I recently saw an article in a popular magazine extolling the virtues of in utero spinal surgery. One mother being interviewed, after elevating the surgeons to deity-like status, indicated that her child was now "fine."
Based on all the experience to date there is no indication that this infant is "fine," but these examples show the status that these ventures have achieved in the lay press and in the public. The above paper does show some potential benefit from early repair in fetuses with lesions above S2. However, the results need to be evaluated objectively. It seems very reasonable to try to reverse or ameliorate the hindbrain herniation, but the reduction in the initial need for shunting may simply result in postponement of the shunt until later, but at some expense. For example, the average time of delivery was 34 weeks, and 3 neonatal deaths occurred as a result of preterm birth. Twenty-two percent had premature rupture of the membranes at an average of 31 weeks requiring hospitalization thereafter. The average time of delivery in those with premature rupture of the membranes was 32 weeks. Although the incidence of oligohydramnios was modest in this study (6%), other studies report a 48% incidence of this finding post-surgery, and all patients require a "hysterotomy" for delivery.1 Cases are springing up of ruptured uteri secondary to the procedure.
Regarding neurological outcome, another group has not reported benefit in neurological function, and in 16% of the infants in the above study the neurological outcome was worse than expected from the anatomic level of the defect.
Actually, many variables get put into play when considering neurological outcome. For example, a study years ago by Luthy et al in the New England Journal of Medicine showed that neurological outcome in infants with neural tube defects (with regard to anatomic level) was better when cesarean sections were performed before labor ensued than when patients had their sections after labor.2 In fact, there was little difference between infants in the latter category and those born vaginally, suggesting that uterine contractions may have had a deleterious effect on neurological outcome. Although the patients in this and other studies had cesarean sections because of the potential for rupture, it was difficult to control for preterm contractions and for early labor (remember the average delivery time was 34 weeks).
The good news is that there is definitely a theoretical advantage to surgical repair and, in fact, the earlier the better. During the procedure the spinal cord, which is stuck to the placode at the superior portion of the defect, is freed up, allowing it to move freely in the canal instead of being tethered. Also, cerebral spinal fluid loss is stopped by closing off the channel into the amniotic cavity. This is why fluid appears to find its way back into the foramen magnum and cisterna magna post-repair. For this reason, and because of the suggestion of reversal of the Arnold Chiari abnormality as noted in the above study, there has been reason enough to initiate a randomized clinical trial supported by the NIH. This is the only way to really test the concept. Historical controls simply will not "cut it," since there are so many "apple and orange" issues to deal with.
In the meantime, appealing to a very vulnerable group of patients in magazines and on the Internet without proper referral should not be condoned.
Dr. Hobbins is Professor and Chief of Obstetrics, University of Colorado Health Sciences Center, Denver.
1. Rintoul NE, et al. Pediatrics. 2002;109:409-413.
2. Luthy DA, et al. N Engl J Med. 1991;324(10):662-666.