What Is Myelomeningocele?
Myelomeningocele (pronounced “my-ello-meningo-seel”), or MMC, is the most severe form of spina bifida. MMC occurs when the protective tube (neural tube) around the spinal cord does not close all the way. The bones and tissue do not form normally. Part of the spinal cord and surrounding nerves stick out through an opening in the skin, exposing them to amniotic fluid.
What Causes Myelomeningocele?
Myelomeningocele occurs in about one in every 2,500 live births in the U.S. The exact cause is unknown. Some research suggests that genes, certain medicines and nutrition may play a role. A baby may be at higher risk if the mother has diabetes while pregnant.
How Is Myelomeningocele Diagnosed?
Myelomeningocele is typically found during a routine prenatal ultrasound between 18 and 22 weeks of pregnancy. A blood test can find the condition as early as 16 weeks. This test screens for maternal alpha-fetoprotein (AFP). AFP in the mother’s blood can show if the baby may have problems.
If doctors are concerned about what they see on the ultrasound or if AFP levels are high, the mother can have more testing to confirm the diagnosis. If the mother decides to have fetal surgery, the doctors will need to perform an “amniocentesis.”
An amniocentesis allows the doctor to take a fluid sample from the sac that surrounds the baby. They can test this fluid for certain “markers” such as AFP. This tells the doctors if spina bifida is present. It can also help determine which kind of defect it is.
Complications of Myelomeningocele
The most serious complications of MMC include:
- Chiari malformation—This is a structural defect in the back of the skull. It allows the back of the brain to settle into the upper portion of the neck. Severe Chiari malformation can cause the baby to have breathing and swallowing problems after birth.
- Hydrocephalus—Our brains have fluid spaces called ventricles. Spina bifida can cause a backup of fluid into these spaces. This condition is called hydrocephalus. It can require more surgeries after birth to drain the fluid.
- Damage to the nerves of the spinal cord—The nerve injury is permanent and irreversible. It can also get worse as the pregnancy progresses.
- Tethered cord—This is scarring of the spinal cord.
In general, the higher the defect is on the spine, the more severe the problems may be. Depending on where the defect is on the spinal cord, the baby may have the following problems after birth:
- Bladder and bowel problems
- Cognitive / learning problems
- Difficulty breathing and swallowing
- Hydrocephalus (buildup of fluid in the brain)
- Inability to walk without help
- Orthopaedic issues, such as club feet
- Sexual dysfunction
- Weakness and loss of feeling below the defect
How is Myelomeningocele Treated?
Until about 25 years ago, there was no way to treat MMC before a baby was born. The only option was to perform surgery after the birth to close the opening in the spine.
Fetal Myelomeningocele Repair
In 2011, doctors began offering a new and exciting alternative: fetal repair surgery. This surgery can significantly lessen spina bifida’s long-term effects.
Fetal repair surgery occurs between 19 and 26 weeks of pregnancy. During surgery, the team:
- Makes an incision across the mother’s abdomen and exposes the uterus.
- Makes an incision through the uterus into the sac around the baby.
- Releases the attachment of the exposed spinal cord.
- Removes the MMC sac if one is present.
- Repairs the spinal defect.
- Covers the spinal cord with a waterproof, protective patch. This protects the spinal cord from exposure to amniotic fluid.
After the procedure, the surgeon closes the mother’s uterus and abdomen. The mother recovers in the hospital for four to five days. Weekly follow-up appointments and ultrasound tests take place to monitor the mother’s and baby’s conditions.
What Are the Potential Benefits of Fetal Myelomeningocele Repair?
In 2011, a landmark research study called the “Management of Myelomeningocele Study (MOMS)” showed that babies who received open fetal repair surgery benefited significantly.
Fetal repair surgery is not a cure. But results from MOMS showed that, compared to surgery after the baby’s birth, fetal repair:
- Cut the risk of hydrocephalus in half
- Increased a child’s chances of walking on their own
- Reversed hindbrain herniation in nine out of 10 patients
A follow-up study in 2020 showed significant physical and emotional benefits in school-age children who received fetal MMC repair surgery.
MOMS also found that fetal MMC repair comes with risks, including the risk of:
- Premature birth (birth earlier than 37 weeks gestation)
- Problems with future pregnancies (more so for patients who undergo the open fetal surgery approach)
- Damage due to the uterus rupturing
Fetoscopic Myelomeningocele Repair: A Less Invasive Option
With these risks in mind, fetal surgeons began to consider alternatives to the “open” approach. A few hospitals, including Cincinnati Children’s, now provide a less invasive in-utero surgery called fetoscopic MMC repair. Cincinnati Children’s began offering this option in 2016.
Fetoscopic repair involves making tiny incisions in the mother’s uterus and inserting three small tubes. The surgical team puts a camera and surgical tools through these tubes to correct the defect.
