By: Bryce
Owen, MD, & Smruti K. Patel, MD, FAANS, FCNS, FACS, FAAP
Myelomeningocele (MMC) is the most severe and common form of spina bifida, a condition that affects how the bones of the spine and spinal cord develop during pregnancy. With myelomeningocele, part of the spinal cord and nerves develop outside of the body through an opening in the bones of the spine. This can affect movement, feeling, bladder and bowel function and other parts of a child’s health.
Children with myelomeningocele are usually cared for by a team of specialists, and because the nervous system changes as a child grows, neurosurgical care often continues throughout childhood and adulthood.
Here's what parents need to know about myelomeningocele and how early diagnosis, careful planning and medical care can help improve health, developmental progress and quality of life.
How does myelomeningocele develop?
Very early in pregnancy, usually within the first month, the brain and spinal cord begin to form. With myelomeningocele, these very early stages are affected when the bones of the spine do not close properly.
As a result, these bones do not fully form, leaving an opening in the back. The spinal cord and nerves may stick out through this opening and stop working . This can cause weakness, paralysis (loss of function) or loss of sensation below the opening in the spine.
Where does myelomeningocele happen?
Myelomeningocele can happen at different levels of the spine. Common locations include:
Lumbar spine (lower back)
Sacral spine (lower spine near the pelvis)
Thoracic spine (upper or middle back)
In general, the higher the MMC is located, the more it affects movement and body function. However, every child is different. The exact effects depend on many things, including the location of the wound, the development of the baby’s brain, and how the spinal cord and nerves developed.
How is myelomeningocele diagnosed?
Many cases of MMC are diagnosed during pregnancy with routine ultrasound exams. If MMC is suspected during pregnancy, families are usually referred to specialists in fetal medicine and high-risk obstetrics where additional testing (such as fetal MRI) is typically done. Early referral allows families to learn about treatment options, discuss delivery planning, consider surgery when necessary, and prepare for newborn care.
Sometimes MMC is diagnosed at birth. The spinal defect is often visible on the baby’s back and may appear as a sac or pouch. After delivery, the medical team works quickly to protect the exposed spinal cord, prevent infection and involve the right teams of doctors and health care providers who can help plan and direct the next steps of the child’s care.
Can myelomeningocele be treated?
Yes, in some cases surgeons can repair myelomeningocele before the baby is born. This is called fetal or prenatal MMC repair. The goal of fetal surgery is to protect the exposed spinal cord earlier in the baby’s development.
Prenatal MMC repair
A landmark clinical trial done in the United States between 2003 and 2010 showed that prenatal repair can reduce some of the health care issues associated with MMC. Patients who received a prenatal repair were not as at risk of hydrocephalus (an abnormal buildup of fluid in the brain that can happen after surgery, causing increased skull pressure) and had better motor function than patients who had had a post-natal surgical repair. Though, pre-natal surgery was also shown to increase risk of preterm birth.Long term brain function of children who have had a prenatal MMC repair are still being studied as these children continue to age. Importantly, fetal surgery does not cure MMC, and these children still require lifelong specialist care.
If MMC is diagnosed after the baby is born (post-natal), the opening in the spine is usually closed within the first few days of life. The purpose of the surgery is to close the opening in the spine, reduce the risk of infection and save brain function. Just like with fetal MMC repair, post-natal repair does not cure MMC, and these children also require lifelong follow up.
How is fetal surgery performed?
This surgery is typically performed during the middle of pregnancy. Two main approaches may be used: Open surgery, which involves opening the uterus through a cut, or fetoscopic repair, where small instruments and cameras are inserted through a tube placed in the uterus. Once the MMC can be seen, the neurosurgeon carefully places the spinal cord and nerves back into the spinal canal and closes the surrounding tissues.
Because fetal surgery is very complicated, families are usually referred to centers with experience in fetal MMC repair and long-term follow-up care. After the surgery, the baby and the mother are monitored closely for any signs of distress. The mother will have frequent check-ups until delivery.
Who may qualify for fetal surgery?
Not all pregnancies are candidates for prenatal repair. Typically, doctors will run tests to confirm the MMC diagnosis and see if a surgery is possible. Fetal surgery can pose big risks for both the parent and baby, including premature birth, tears in the uterus, maternal bleeding or infection and the need for a C-section. Families should have detailed discussions with experienced fetal surgery teams when considering this option.
How is post-natal surgery performed?
Post-natal surgery is performed similarly to pre-natal or fetal surgeries. The care team may perform an MRI or ultrasound to better understand the specifics of the MMC, and the surgery is typically done within 72 hours after the baby is born.
After surgery, babies are monitored closely for wound healing, breathing and feeding issues, and development of hydrocephalus (an abnormal buildup of fluid in the brain that can happen after surgery, causing increased skull pressure). Some babies remain in the NICU for days or weeks, depending on their medical needs.
Does myelomeningocele require lifelong care?
Yes. Children with MMC need lifelong follow-up because the nervous system and spine continue to change as they grow. Regular monitoring helps identify problems early and may improve long-term outcomes. Some children may need more surgeries during childhood or adolescence to help address related conditions that occur because of MMC, whether they had a prenatal or postnatal MMC repair. of
Are there other conditions related to myelomeningocele that require surgery?
MMC can affect many aspects of a child’s nervous system.
Chiari II malformation
ost children with MMC have a condition called Chiari II malformation. This causes parts of the brain near the base of the skull to be pulled downward into the upper spinal canal. This can sometimes affect swallowing, breathing, feeding, voice or crying, though many children never develop symptoms.
A type of surgery can be done to remove a small amount of bone at the base of the skull to relieve pressure on the brain stem. Because these symptoms can develop in infancy and may be life-threatening, all infants with MMC should be monitored closely.
Hydrocephalus
Many children with MMC develop hydrocephalus, which is a buildup of cerebrospinal fluid inside the brain. This extra fluid can increase pressure within the brain if left untreated. Hydrocephalus may develop before or after birth.
Signs of hydrocephalus in infants include:
fast head growth
bulging fontanelle (a baby’s "soft spot" on the head)
vomiting
sleepiness
fussiness or irritability
eyes that stay looking downward
Some children require surgery to divert or control the buildup of cerebrospinal fluid. Treatment options may include placing a shunt (a small tube that redirects fluid away from the brain and into a different part of the body where it can be safely absorbed) or an endoscopic third ventriculostomy (ETV), where a small hole is made in the brain to allow fluid to be absorbed by a different part of the brain.
Both approaches can come with complications. Shunts require lifelong monitoring. They can fail (become blocked or over-drain) or become infected, requiring surgery to fix it. Signs of a shunt failing include new or worsening headaches, irritability, vomiting, or vision changes. These are medical emergencies and patients or caregivers should contact your care team immediately if you notice these symptoms in a child with a shunt.
ETV avoids implanting a permanent shunt device, eliminating the risk of shunt malfunction and infection. However, it is not always the best fit for all patients, and it carries its own risks and failure rate.
Your child’s neurosurgical team will help determine which treatment, if any, is best.
Tethered cord
As children grow, scar tissue or tight attachments around the spinal cord can place tension on the nerves. This is called a tethered cord.
Symptoms may include:
new leg weakness (especially after a growth spurt)
changes in walking
back or leg pain
worsening spine curving (scoliosis)
changes in bladder or bowel function
Surgery (tethered cord release or untethering) may be recommended when symptoms develop or worsen. Because retethering can happen at any time, families should watch for these signs throughout childhood and adolescence, especially as your child goes through growth spurts, which can increase risk of the cord re-tethering.
Can myelomeningocele be prevented?
Yes. Folic acid, a B vitamin, can help prevent the development of MMC when taken before and during pregnancy. MMC develops during the first few weeks of pregnancy, often before the parent knows they are pregnant. The American Academy of Pediatrics (AAP) recommends that all people who can become pregnant take 400 micrograms (mcg) per day of folic acid.
What is the outlook for children with MMC?
The outlook for children with MMC has improved significantly due to advances in neonatal medicine, obstetrics, neurosurgery, rehabilitation, urology, orthopedic surgery and coordinated care. Many children with MMC can attend regular school, participate in sports and activities, develop wonderful friendships and relationships, and eventually transition to independent adult lives.
Know that you are not alone. Long-term partnerships with medical teams, therapists, schools and community resources can help children with MMC reach their full potential.
About Dr. Owen
Bryce Owen, MD, is a medical resident/fellow in the Department of Neurosurgery at the University of Cincinnati College of Medicine.
About Dr. Patel
Smruti K. Patel, MD, FAANS, FCNS, FACS, FAAP, is a neurosurgeon at Cincinnati Children’s Hospital Medical Center and an associate professor in the Department of Neurosurgery at University of Cincinnati College of Medicine.