Open Spina Bifida / Myelomeningocele

Background

Open spina bifida occurs in approximately 1 in 1,500 births annually in the United States. Open spina bifida develops when the spine fails to close at some point along its length during fetal development. Failure of the vertebrae, the bony part of the spinal column, to close around the spinal cord results in different forms of spina bifida. Myelomeningocele (MMC) is the most common type and occurs when both the meninges (membranous coverings) and the spinal cord protrude through the spinal defect. Myeloschisis is the most severe type and occurs when the spinal cord protrudes with no meninges covering the defect. These forms of spina bifida are oftentimes accompanied by a condition known as Arnold Chiari II Malformation, or herniation of the hindbrain (brain stem). When cerebral spinal fluid (CSF) escapes from the open spinal defect, it causes the hindbrain to descend into the spinal canal. This blocks CSF circulation and may lead to hydrocephalus, or accumulation of CSF in the brain.

MMC leads to injury and loss of spinal cord tissue at and below the defect. The abnormal spinal cord development, intrauterine trauma, and the toxic exposure to amniotic fluid may contribute significantly to the newborn’s neurological status (“two-hit hypothesis”). Because of these in-utero factors, fetuses with open spina bifida may benefit from correction before birth to improve function after birth.

In 2003, the NIH sponsored a multi-center randomized controlled trial of in utero repair of MMC vs. standard neonatal repair, the Management of Myelomeningocele Study (MOMS), the results of which were published in 2011. Prenatal repair resulted in reduction of the need of shunting at 12 months of age, decreased rate of hindbrain herniation by one-third at 12 months, doubling of the ability to ambulate without the assistance of orthotics, and produced a level of function that was two or more levels better than expected according to anatomic levels. However, the in utero repair was performed via open maternal-fetal surgery, which means the mother’s abdomen is opened (laparotomy) and her uterus is opened (hysterotomy), and was associated with significant risks, including higher rates of preterm birth, fetal bradycardia, oligohydramnios, placental abruption, pulmonary edema, maternal transfusion at delivery, and a 35% risk of uterine thinning or dehiscence or rupture. Furthermore, the legacy of open in utero repair in regards to a patient’s future pregnancies is an approximately 28% risk of uterine dehiscence or rupture.

Our group has worked on developing a minimally-invasive technique (so-called ‘keyhole surgery’) for the antenatal treatment of MMC, translating an experience of more than 10 years in the animal model to a viable clinical application. The technique developed by our group does not require hysterotomy (uterine incision). Rather, small instruments are placed into the womb through tiny incisions, and with the use of partial CO2 insufflation, the open spina bifida is repaired. This approach minimizes the risks of the surgery for the mother, while preserving the potential benefits of the in utero repair for the fetus.

The following management options will be offered to all eligible patients.

Management Options

1. Expectant management with standard postnatal repair. This option provides minimal maternal risks and low risk of preterm birth. Yet, it may result in progressive deterioration of nerve tissue due to continued intrauterine trauma and exposure to the toxic effects of amniotic fluid.
2. Termination of pregnancy.
3. Prenatal repair of the myelomeningocele via open maternal fetal surgery. This approach requires maternal laparotomy and hysterotomy, under deep general anesthesia. This is the approach used in the Management of Myelomeningocele Study (MOMS).
4. Fetoscopic prenatal repair. The primary benefit of this approach is the lessened maternal risks as compared to the open maternal fetal surgical approach. Also, vaginal delivery is acceptable for this and future pregnancies. There are two fetoscopic techniques, percutaneous and laparotomy/uterine exteriorization, described below.

Who is a Candidate for Surgical Treatment?

Inclusion Criteria

1. Myelomeningocele (including myeloschisis) beginning at level T1 through S1 with hindbrain herniation
2. Maternal age ≥18 years
3. Gestational age of 19 to 27 6/7 weeks
4. Normal karyotype and/or microarray
5. Normal echocardiogram
6. Positive evaluation of social work consult
7. Positive evaluation from pediatric neurology consult
8. Willing to remain in the area for post-surgical follow-up and delivery, and be willing to return to our center for postdelivery evaluations.

Exclusion Criteria

1. Multiple gestation
2. Insulin-dependent pre-gestational diabetes
3. Presence of a fetal anomaly not related to myelomeningocele
4. Fetal kyphosis ≥ 30 degrees
5. Presence of uterine cervical cerclage or incompetent cervix
6. Placenta previa or placental abruption
7. Short cervix < 25 mm
8. BMI of 40 or greater
9. History of preterm delivery prior to 37 weeks
10. Maternal-fetal Rh isoimmunization, Kell sensitization, or neonatal alloimmune thrombocytopenia
11. Maternal HIV, Hepatitis-B, Hepatitis-C status positive
12. Negative psychosocial evaluation as determined by the social worker

Details of Procedure

We offer two fetoscopic approaches to correcting the open spina bifida defect, both of which require general anesthesia and a 2-day inpatient stay:

1. Direct percutaneous – In the minimally-invasive direct percutaneous method, 3-4 ports are placed percutaneously through the maternal abdomen and uterus. Amniotic fluid is removed and CO2 is placed into the womb. Dissection around the placode allows the placode to drop into the spinal canal. A dura patch is placed over the defect and the skin (and underlying muscle if possible) is reapproximated and sutured over the patch. If there is insufficient amount of skin to cover the defect, a secondary (skin) patch will be sutured into the skin to create a watertight seal (See Video below). Postoperative recovery is relatively quick and there is no laparotomy scar. Yet, this approach is associated with a relatively increased risk of preterm premature rupture of membranes (PPROM) and preterm birth.
2. Laparotomy/Uterine exteriorization. In the laparotomy and uterine exteriorization method, an incision is made into the abdominal cavity and the uterus is exteriorized (removed out of the maternal abdomen). Two to three ports are placed through the exteriorized uterus and the procedure proceeds as previously described. The approach is associated with relatively increased postoperative recovery, a laparotomy scar, and possibly a higher anesthetic risk. Yet, this approach is associated with relatively decreased risk of PPROM and preterm birth.

Percutaneous Fetoscopic Closure of Open Spina Bifida Defect

Postoperative Care

You will remain in the hospital for about 2 days after surgery. You will then be sent home and asked to maintain minimal physical activity. This entails remaining at home for the duration of your pregnancy, except for doctor visits. You will have alternate follow-up visits between our office and your referring maternal-fetal medicine doctor every 1-2 weeks. You will also have a follow-up fetal MRI about 4 weeks after surgery. You may be given the option of a vaginal delivery, based on obstetric indications. Following delivery, your baby will be transferred to Children’s Hospital Los Angeles (CHLA) for management. Postnatal testing will be performed at CHLA at 6, 12, 24, 30, 48, and 60 months of age.

For further reading, please see the link below:

Los Angeles Fetal Surgery Publications