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Spina Bifida

Neural tube defect causing incomplete spinal canal closure with variable paralysis

ICD-10: Q05.9 · congenital condition

Spina bifida is a neural tube defect (NTD) resulting from incomplete closure of the neural tube during the third to fourth week of embryonic development. It encompasses a spectrum of conditions: spina bifida occulta (a bony defect without neural involvement, usually asymptomatic), meningocele (protrusion of meninges without neural tissue), and myelomeningocele (MMC) — the most severe and common form, in which the spinal cord and nerve roots protrude through the bony defect in a sac on the baby's back. Neural tissue exposed to amniotic fluid during fetal development suffers progressive damage, causing motor paralysis and sensory loss below the defect level at birth. Myelomeningocele occurs at an incidence of approximately 3 per 10,000 live births in the United States. Folic acid supplementation before conception and in early pregnancy reduces the risk by approximately 70%. Maternal diabetes, obesity, and antiepileptic drug use (particularly valproic acid) increase risk. The condition is associated with Chiari II malformation (hindbrain herniation) in nearly all MMC cases, hydrocephalus requiring shunting in 80–90%, and tethered cord syndrome. Myelomeningocele repair is performed within 24–72 hours of birth to prevent infection and limit further neural damage. Fetal repair (in utero MMC closure between 19 and 26 weeks gestation) — shown in the landmark MOMS trial to reduce shunting rates and improve motor outcomes — is now offered at specialized fetal surgery centers. Lifelong multidisciplinary management addresses paralysis, bladder and bowel dysfunction, orthopedic complications, hydrocephalus, and educational and cognitive needs.

Anatomy & Pathology

During weeks 3–4 of embryonic development, the flat neural plate folds inward to form the neural tube, which eventually becomes the brain and spinal cord. Closure normally begins in the cervical region and proceeds bidirectionally. Failure of closure in the caudal portion — the lumbosacral end — produces the open myelomeningocele. In this defect, the vertebral arches fail to fuse posteriorly, the meninges herniate outward, and neural elements are tethered and exposed at the skin surface.

Symptoms

  • Paralysis or weakness of the legs at and below the defect level (visible at birth)
  • Sensory loss below the lesion — risk of pressure injuries and burns
  • Neurogenic bladder and bowel: urinary retention, incontinence, constipation
  • Hydrocephalus from associated Chiari II malformation (affects 80–90%)
  • Tethered cord causing progressive neurological loss with growth
  • Orthopedic deformities: clubfoot, hip dysplasia, scoliosis
  • Cognitive and learning differences in a subset of patients, particularly with shunted hydrocephalus

Causes & Risk Factors

  • Folic acid deficiency during neural tube closure (3–4 weeks post-conception)
  • Maternal valproic acid or carbamazepine use during embryogenesis
  • Maternal diabetes mellitus and obesity
  • Genetic predisposition — recurrence risk 3–5% after one affected child
  • Hyperthermia during early pregnancy (fever or hot tub use)

Treatment Options

Conservative

  • Clean intermittent catheterization (CIC) for neurogenic bladder — primary bladder management from infancy
  • Orthotics (AFOs) and physical therapy for ambulation maximization based on lesion level
  • Bowel management program: timed evacuation, dietary fiber, laxatives

Surgical

  • Myelomeningocele closure within 24–72 hours of birth (or fetal surgery at 19–26 weeks at specialized centers)
  • Ventriculoperitoneal (VP) shunt or endoscopic third ventriculostomy (ETV) for hydrocephalus
  • Tethered cord untethering surgery when progressive neurological deterioration occurs with growth

When to see a spine specialist

Spina bifida is diagnosed prenatally by maternal AFP screening and anatomy ultrasound, or at birth for undiagnosed cases. Any child with known spina bifida who develops new weakness, new scoliosis, worsening bladder function, or signs of Chiari (stridor, apnea, upper extremity weakness) requires urgent neurosurgical evaluation for shunt malfunction, tethered cord, or Chiari decompensation.

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Frequently Asked Questions

Can spina bifida be detected before birth?

Yes. Maternal serum alpha-fetoprotein (AFP) screening at 15–20 weeks gestation is elevated in open neural tube defects. Second-trimester anatomy ultrasound detects the characteristic "lemon sign" (scalloped frontal bones) and "banana sign" (Chiari II cerebellar herniation) with high sensitivity. Amniocentesis can confirm elevated amniotic AFP and acetylcholinesterase. Fetal MRI provides detailed anatomical characterization. Prenatal diagnosis allows planning of delivery at a center capable of immediate neonatal surgical closure and referral to a fetal surgery program if criteria for fetal repair are met.

What level of spina bifida allows walking?

Ambulatory potential is strongly predicted by lesion level. Sacral-level lesions (S2–S5): community ambulation with minimal or no assistive devices. Low lumbar (L4–L5): community ambulation with orthotics (AFOs). Mid-lumbar (L3): household ambulation with forearm crutches and AFOs; wheelchair for community distances. High lumbar (L1–L2) and thoracic levels: primarily wheelchair users. Even non-ambulatory individuals benefit from standing and therapeutic ambulation for bone density, urodynamics, and pressure relief.

Do adults with spina bifida have complications later in life?

Yes. Spina bifida is a lifelong condition with evolving medical needs. Adults face higher rates of shunt malfunction than children (shunts can function normally for years before failing). Tethered cord re-tethering causes progressive neurological decline in adulthood. Urological complications — renal damage from chronic neurogenic bladder — are a major source of late morbidity and require continued urological surveillance. Obesity, depression, social isolation, and reduced employment are common. Transition from pediatric to adult care requires multidisciplinary coordination.

Related Conditions

Sources

  1. Adzick NS, et al. A randomized trial of prenatal versus postnatal repair of myelomeningocele (MOMS trial). N Engl J Med. 2011.
  2. Copp AJ, et al. Spina bifida. Nat Rev Dis Primers. 2015.