Myelomeningocele & Neural Tube Defects

What is myelomeningocele & what are neural tube defects?

A “spectrum” of congenital anomalies, ranging from severe open defects to milder closed malformations that may be discovered later in life.

The neural tube is the embryologic structure from which the brain and spinal cord develop. If it fails to close normally during the first weeks of gestation, so-called neural tube defects occur.

Myelomeningocele is the most severe open spinal defect: the spinal cord is exposed at the surface as a flattened placode and is not protected by bone, meninges, or skin. It most commonly involves the lumbosacral region and is associated with motor and urologic deficits.

Other neural tube defects may be closed (covered by skin), such as lipomyelomeningocele, myelocystocele, split cord malformations, and tethering of the filum terminale by lipomas. These are often associated with tethered cord syndrome.

How does the neural tube develop & why do these defects occur?

From the “neural groove” to formation of a closed neural tube—what happens when closure fails?

During days 20–25 of gestation, the neural groove deepens and the neural folds fuse, forming the closed neural tube, which then separates from the overlying ectoderm. If closure fails in the spinal region, an open defect such as myelomeningocele remains.

The causes are multifactorial (genetic and environmental). Adequate intake of folic acid (400 μg/day) before conception and during early pregnancy significantly reduces the risk of open neural tube defects. Nevertheless, some cases still occur despite appropriate prevention.

When the defect is small and covered by skin, it is classified as a closed defect. In such cases, AFP levels may not be elevated, and the fetus may reach birth without clear warning signs on routine prenatal screening.

How is prenatal diagnosis made?

A combination of maternal serum screening, ultrasound, and—when necessary—fetal MRI.

In most pregnancies today, myelomeningocele is diagnosed prenatally. Screening typically includes:

• Maternal alpha-fetoprotein (AFP) testing in the second trimester, which is sensitive for open neural tube defects but not fully specific.
• Level II ultrasound, which identifies the spinal defect and often indirect signs of Chiari II malformation (small posterior fossa, characteristic cranial shape, etc.).
• When indicated: amniocentesis for AFP/acetylcholinesterase in amniotic fluid and/or fetal MRI for detailed evaluation of the brain and spine.

When AFP is not elevated and there are no Chiari II features, closed neural tube defects are often confirmed only after birth.

What is the relationship with Chiari II malformation & hydrocephalus?

Myelomeningocele affects not only the spine but also brain structure and cerebrospinal fluid dynamics.

Nearly all children with myelomeningocele demonstrate imaging features of Chiari type II malformation: downward displacement of the cerebellum and medulla through the foramen magnum, a small posterior fossa, and often distortion of the brainstem.

Clinically, only about 10% develop symptoms severe enough to require surgical decompression (swallowing difficulties, stridor, apneic episodes, worsening quadriparesis or scoliosis, progression of syringomyelia).

In addition, approximately 90% of children with postnatally repaired myelomeningocele develop hydrocephalus and require permanent CSF diversion (most commonly a ventriculoperitoneal shunt). Shunt malfunction may present with “Chiari-like” symptoms; therefore, any suspected Chiari syndrome must first prompt evaluation of shunt function.

What does this mean functionally for the child?

Mobility, sensation, bladder and bowel control, learning—what is the realistic long-term outlook?

Functional prognosis depends primarily on the level of the lesion along the spine (e.g., T12, L3, S1):

• Children with lesions below L3 often achieve ambulation, with or without orthotic support.
• The higher the lesion, the more likely the need for a wheelchair.
• Urologic dysfunction (neurogenic bladder) is nearly universal and requires pediatric urology follow-up, often intermittent catheterization and tailored medical management.

Regarding cognitive function, a substantial proportion of children have normal or near-normal intelligence; however, approximately one-quarter may exhibit lower IQ or selective learning difficulties, particularly when hydrocephalus and multiple surgeries are present.

How is it managed after birth—first steps & surgery?

The first hours and days are critical for protecting the spinal cord and preventing infection.

After birth, the primary objective is to protect the neural placode and close the defect as soon as possible:

• The newborn is placed in the prone position to avoid pressure on the lesion.
• The placode is covered with sterile, moist dressings.
• Prophylactic antibiotics are administered.
• A comprehensive neonatal and neurosurgical assessment is performed, documenting muscle strength, limb deformities, and cranial ultrasound to evaluate for hydrocephalus.

Surgical closure of the myelomeningocele is usually performed within the first 72 hours of life. The placode is carefully dissected from surrounding tissues, reconstructed into a closed neural tube, and covered with new dura, muscle, and skin. Large defects may require plastic surgical techniques with local flaps.

If hydrocephalus is already evident, a CSF shunt may be placed during the initial operation or in a staged fashion, depending on the clinical condition.

What is fetal (in utero) surgical repair?

A pioneering option for selected cases that may improve neurological outcomes but carries significant risks.

In recent years, specialized centers have performed fetal surgical closure of myelomeningocele, typically at 24–26 weeks’ gestation. The uterus is exteriorized, a controlled hysterotomy is performed, the fetal back lesion is exposed, and microsurgical closure is carried out.

Level I evidence demonstrates that fetal repair:

• significantly reduces the need for permanent hydrocephalus shunting,
• on average improves motor function compared with postnatal repair,
• may lessen the severity of Chiari II malformation.

However, it is associated with increased risks of preterm birth, uterine rupture, and complications for the mother and future pregnancies. Candidacy is determined only at specialized centers, following extensive counseling with pediatric neurosurgeons, obstetricians, and neonatologists.

What is tethered cord & what are closed defects?

When the spinal cord is abnormally anchored, progressive neurological symptoms may develop, often later in childhood.

Tethered cord syndrome refers to a constellation of symptoms caused by abnormal traction on the spinal cord. It may be associated with:

• Lipomyelomeningocele (a dermolipomatous mass tethering the cord),
• Myelocystocele (a cystic dilation of the distal spinal cord),
• Split cord malformations (division of the cord into two hemicords),
• Tethered filum terminale (thickened or fatty filum),
• Dermal sinuses with deep extension.

Symptoms raising concern for tethered cord include:

• intermittent low back or thigh pain,
• weakness or sensory changes in the legs,
• progressive scoliosis or foot deformities (e.g., pes cavus),
• new or worsening urinary dysfunction,
• neurogenic constipation.

Careful inspection of the skin over the spine is essential: localized lipomas, hypertrichosis, hemangiomas, dimples, or cutaneous anomalies may conceal an underlying defect. Treatment is surgical detethering, often performed in infancy or childhood.

In more complex cases (lipomyelomeningocele, previously repaired myelomeningocele), repeat detethering may be required due to retethering as the child grows.

What other cranial neural tube defects exist?

In some cases, the defect involves the skull—ranging from lethal conditions to surgically correctable anomalies.

Anencephaly

A severe defect caused by failure of closure of the anterior neuropore. Large portions of the brain and skull are absent; this condition is incompatible with life.

Encephalocele

Herniation of meninges and often dysplastic brain tissue through a cranial bone defect, most commonly in the occipital or frontal region, covered by thin skin. Treatment consists of surgical excision of nonviable tissue and reconstruction of the meninges and skull. Prognosis depends on size, location, and associated hydrocephalus.

Cranial dermal sinuses

Epithelial-lined tracts connecting the skin to the intracranial compartment, often in the frontal or occipital region. They may be subtle or present after infection. Complete surgical excision is required to prevent meningitis or dermoid cyst formation.

What are the possible complications & the long-term course?

Myelomeningocele is a lifelong condition requiring continuous support and coordinated multidisciplinary care.

Potential complications and long-term issues include:

• Hydrocephalus & shunt malfunction (infection, obstruction, overdrainage).
• Chiari II malformation & syringomyelia requiring posterior fossa decompression.
• Retethering of the cord with deterioration in motor or urologic function.
• Orthopedic problems such as scoliosis, foot deformities, and hip dislocations.
• Urologic & renal complications if neurogenic bladder is inadequately managed.
• Pressure ulcers in areas of reduced sensation.
• Psychological & social challenges for the child and family.

Despite these challenges, many children and adolescents with myelomeningocele, with appropriate medical care, can lead active and productive lives, pursue education and employment, and develop strategies for independence and adaptation.

Practical issues & long-term care planning for families

From intensive care to home, school, and adulthood—the journey is a marathon.

Care for a child with myelomeningocele requires a multidisciplinary team: pediatric neurosurgeon, pediatric neurologist, pediatric urologist, orthopedist, physical therapist, occupational therapist, nephrologist, psychologist/child psychiatrist, and social worker.

In practice, families must organize:

• regular visits for shunt surveillance & spinal growth monitoring,
• urodynamic studies, renal function monitoring, and training in intermittent catheterization,
• physical therapy & orthopedic supports (braces, wheelchair),
• school accommodations & access to special education services when needed,
• psychological support for the child, siblings, and parents.

At Neuroknife, we emphasize providing a consistent point of reference for families—a team that coordinates appointments, periodically reassesses the overall care plan, and supports a smooth transition into adulthood.