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PubMed This is a summary of 24 peer-reviewed journal articles Updated
Pediatric Neurosurgery · Myelomeningocele

Understanding the Diagnosis: Myelomeningocele

At a Glance

Myelomeningocele is an open form of spina bifida in which the spinal cord and nerves protrude through an opening in the spine. A child’s mobility depends on the lesion level and postnatal nerve function, while hydrocephalus risk and treatment needs are assessed by a team of specialists.

Receiving a diagnosis of myelomeningocele can feel overwhelming, but it is a moment that begins a journey of specialized, proactive care. While this is a serious condition, advancements in pediatric neurosurgery and multidisciplinary care mean that children born with this diagnosis today have access to treatments and supports that were unavailable in previous generations [1][2]. Understanding the biology and the road ahead can help replace panic with a focused plan for your child’s future.

What is Myelomeningocele?

Myelomeningocele (pronounced my-el-o-men-in-go-seal) is the most severe and common open form of spina bifida, a type of open neural tube defect [3]. In plain language, “open” means the spinal cord and its protective coverings do not form a complete circle of bone and skin around the nerves. Instead, a sac-like protrusion containing the spinal cord and nerves pushes through an opening in the baby’s back [3].

Because the spinal cord is not fully enclosed, the delicate nerve tissue is exposed to amniotic fluid during pregnancy. This exposure can cause progressive injury to the nerves over time [4][5].

How the Spinal Tube Folds

The human nervous system begins as a flat plate of cells that must roll up into a tube, much like a piece of paper rolling into a cylinder. This process, called neurulation, happens very early—typically between the third and fourth week after conception, often before a person even knows they are pregnant [1][6].

In myelomeningocele, the “zipper” that closes this tube fails to join completely at the bottom (caudal) end of the spine [1][7]. This is a complex biological event influenced by a mix of genetics and environmental factors, and in most cases, it is not caused by a single factor or anyone’s “fault” [8][9].

Known Risk Factors

While the exact cause for any individual child is often unknown, researchers have identified several factors that can increase the likelihood of a neural tube defect. It is crucial to understand that having these risk factors does not mean a parent caused the defect.

  • Folate Levels: Low levels of folate (Vitamin B9) are a major risk factor. Taking 400 μg of folic acid daily before and during early pregnancy is the standard recommendation for prevention [10][11]. However, if a family has had a previous pregnancy affected by a neural tube defect, clinicians often recommend a much higher dose (up to 4 mg) under medical supervision. Note: Taking folic acid after the neural tube has failed to close will not repair an established defect.
  • Maternal Health: Pre-existing conditions such as diabetes (Type 1 or Type 2) or a high Body Mass Index (BMI) are associated with higher risk [12][13].
  • Medications: Certain anti-seizure medications, particularly valproic acid, are known teratogens [14]. Never stop or alter an antiseizure medication without explicit guidance from your doctor, as seizures pose severe risks to both mother and baby.
  • Genetics: If a close relative has a neural tube defect, the risk for future pregnancies may be higher, though most cases occur in families with no prior history [13][15].

Predicting Movement and Mobility

One of the first questions parents ask is, “Will my child walk?” The answer depends on several factors, including the lesion level (the point on the spine where the opening occurs), postnatal care, physical therapy, and the presence of other issues like tethered cord or hydrocephalus. The vertebral level is only a broad tendency, not an exact predictor [16][17].

Lesion Level Anatomic Location Broad Tendencies for Mobility
Thoracic Chest / Mid-back Often relies on a wheelchair as the primary mode of mobility [16].
Lumbar Lower back Variable hip and knee movement; often uses braces (orthotics) and walkers or crutches [18][17].
Sacral Tailbone area Strong hip and knee movement; highest likelihood for independent walking, often with ankle braces [19][18].

Fetal movement seen on a prenatal ultrasound provides a helpful snapshot, but it is not a perfect guide. A formal postnatal functional neurological exam is much more informative [20][21].

Understanding Hydrocephalus Risk

Many children with myelomeningocele develop hydrocephalus, a condition where extra fluid builds up in the brain’s fluid-filled spaces (ventricles). This often happens because of a Chiari II malformation, where the lower part of the brain is pulled slightly toward the spinal canal, blocking the normal flow of fluid [1][22].

The risk of needing a shunt (a small tube to drain excess fluid) is associated with how large the ventricles appear on prenatal scans, though no single measurement decides treatment:

  • Ventricles <10 mm: Lower risk for a shunt [23].
  • Ventricles 10-15 mm: Intermediate risk.
  • Ventricles ≥15 mm: Higher risk for a shunt and may influence the expected benefit of prenatal surgery [23][24].

A Team-Based Approach

Because myelomeningocele affects multiple systems—the brain, the spine, the bladder, and the legs—your child will be cared for by a multidisciplinary team. This team usually includes neurosurgeons, urologists, orthopedic surgeons, and physical therapists who work together from day one to provide your child with the best possible functional outcomes [1]. While the diagnosis is lifelong, the goal of modern care is to maximize independence and quality of life.

Common questions in this guide

What exactly is myelomeningocele?
Myelomeningocele is the most severe and common open form of spina bifida. The spinal cord and its protective coverings protrude through an opening in the spine, leaving nerve tissue vulnerable to injury during pregnancy.
Does myelomeningocele mean my child will not walk?
Not necessarily. Mobility varies with the level of the spinal opening, the child's nerve function after birth, physical therapy, and problems such as tethered cord or hydrocephalus. A postnatal neurological examination usually provides more useful information than prenatal movement alone.
How likely is my baby to need a shunt for hydrocephalus?
Many children with myelomeningocele develop hydrocephalus, in which extra fluid collects in spaces inside the brain. Larger ventricles on prenatal scans are linked with a greater chance of needing a shunt, but the measurement is only one part of the decision and no single number determines treatment.
What can increase the chance of myelomeningocele?
Risk factors include low folate levels, maternal diabetes, a high maternal body mass index, certain antiseizure medicines such as valproic acid, and a close family history of neural tube defects. Having a risk factor does not mean a parent caused the condition, and most cases occur without a previous family history.
Which specialists will care for a baby with myelomeningocele?
Care is usually coordinated by a team that may include a neurosurgeon, urologist, orthopedic surgeon, and physical therapist. These specialists address the brain and spine, bladder, bones and joints, movement, and long-term independence.
Can surgery be done before birth for myelomeningocele?
Prenatal surgery may be considered for some pregnancies at specialized centers. The team reviews the baby's imaging, including the lesion and brain fluid spaces, as well as the mother's health and the program's eligibility criteria; ask how these findings compare with criteria used in the MOMS trial.
Did I cause my baby's myelomeningocele?
Usually, no single cause can be identified. Neural tube closure reflects a complex mix of genetic and environmental factors, and risk factors such as low folate or certain health conditions do not mean a parent is to blame.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is the precise anatomic level of my baby's lesion, and how does it currently compare to the functional movement you see on ultrasound?
  2. 2.Based on the initial measurements of the brain's fluid spaces (ventricles), what is the estimated risk that my child will need a shunt or other fluid-management procedure?
  3. 3.Are there any other findings in the brain, spine, or other organs that I should know about, or is this an 'isolated' diagnosis?
  4. 4.What team of specialists—such as neurosurgeons, urologists, and physical therapists—will be involved in my child's care immediately after birth?
  5. 5.If we are considering prenatal surgery, how do my child's specific measurements compare to the criteria used in the MOMS trial?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

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This page is for informational purposes only and does not constitute medical advice. Your fetal-care and pediatric specialists should interpret your baby's imaging, lesion level, and treatment options.

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