The Operation for Fetal Myelomeningocele Repair

Patient Positioning

• Lithotomy position: After induction, the patient is placed in the lithotomy position to optimize surgeons’ access to the pelvic region.

Multispecialty surgical care: Four or more surgeons must access the patient’s pelvic region, requiring a coordinated teamwork approach. Team members include pediatric neurosurgery, maternal fetal medicine, plastic surgery, and/or pediatric surgery specialists. (Image used with permission and archived by the Fetal Center at Vanderbilt.)

Surgical Approach

Exposure of the spinal defect is performed by either MFM surgery or pediatric surgery specialists.

• Skin incision: Using a scalpel, then monopolar coagulation, a vertical incision is made from the pubis to just above the umbilicus to expose the uterus.
• Hysterotomy: Ultrasonic guidance is used to ensure the ~7 cm hysterotomy incision avoids the placenta but prioritizes proximity to the myelomeningocele sac.
• Uterine suturing: Extreme care is taken to avoid disruption of fetal membranes while the uterine lining is sutured up to the edge of the exposed uterine wall and expanded to expose the spinal defect.
• Fetal anesthesia: Fentanyl and vecuronium are administered IM to the fetus, while echocardiography ensures stable fetal hemodynamics.

Securing the uterine wall: After hysterotomy, the uterine wall is mobilized, sutured, and widened to allow access to the fetus. (Image used with permission and archived by the Fetal Center at Vanderbilt.)

Exposure of the spinal defect: Under ultrasonic guidance and via manual manipulation, the fetal spinal defect is situated in the middle of the hysterotomy site. At this point, the neurosurgical portion of the operation begins. (Image used with permission and archived by the Fetal Center at Vanderbilt.)

Intervention

The pediatric neurosurgeon performs closure of the spinal defect. The basic tenets of postnatal myelomeningocele repair apply for standard open fetal closure with only few differences.

• Placode release: Under loupe magnification, the junctional zone is incised sharply with micro scissors, and the placode is permitted to descend into the native spinal canal.
• Dural mobilization and closure: The dura is mobilized at its interface with the more lateral lumbodorsal fascia, reflected over the placode, and closed with a running suture. Alternatively, a synthetic dural substitute is placed above the placode and tucked under the fetal skin edges.
• Fascial closure: Some advocate mobilization of the lumbodorsal fascia and closure in the midline over the placode. Although this strategy is feasible and may be reasonable in patients with an incompetent dural closure or tenuous graft, it is not routinely performed at all centers.
• Skin closure: The skin is mobilized by suprafascial dissection laterally over the flank. The edges are brought together and closed in a watertight fashion with a running absorbable suture. If tension in the midline closure is deemed by the neurosurgeon or plastic surgeon to be too great, one or two relaxing flank incisions can be created. Thus, a bipedicled flap prioritizes a tensionless midline closure. A dermal allograft is then sewn in to replace the lateral space(s) created by the relaxing incision.

Placode release: Sharp incision of the transitional zone between the placode and fetal dermis decompresses the CSF sac and allows descent of the placode into the native spinal canal. (Image used with permission and archived by the Fetal Center at Vanderbilt.)

Dural substitute: Incompetent or friable dura that precludes watertight closure mandates a synthetic dural substitute (artificial tissue patch, indicated by blue arrow) be onlayed to cover the placode. (Image used with permission and archived by the Fetal Center.)

Fetal skin closure: After mobilizing the skin edges, a single running absorbable suture is used to close the skin in the midline over the dura/graft complex. (Image used with permission and archived by the Fetal Center at Vanderbilt.)

Closure

• Close skin (fetus): The pediatric neurosurgeon uses a single running absorbable suture to close the skin in the midline over the dura/graft complex.
• Close uterus, abdominal wall, and skin (mother): After fetal skin closure, primary management is passed back to the obstetric team. The uterus is closed in layers, followed by the abdominal fascia and the skin in standard fashion.

Uterus and skin closure: Closure of the uterus, abdominal wall, and skin is conducted by the obstetric surgery team. (Image used with permission and archived by the Fetal Center at Vanderbilt.)