Neural tube defects

Last updated: December 23, 2022

Summarytoggle arrow icon

Neural tube defects (NTDs) are the most common congenital malformations of the central nervous system (CNS). They develop between the 3rd and 4th week of pregnancy and are often caused by folate deficiency. Most commonly, a deficiency in folate results in improper closure of the neural tube in the embryo, mainly at the caudal or cranial ends. The formation of defects at the caudal end is more common and is known as spina bifida. Spina bifida may occur without any apparent clinical features (spina bifida occulta) or manifest with protrusion of the meninges and, potentially, the spinal cord (myelomeningocele) through a gap in the vertebrae. Myelomeningoceles predominantly cause symptoms of sensory and motor function loss, such as bladder dysfunction and paraplegia. NTDs at the cranial end can cause cranial fissure malformations; the most severe manifestation of this, anencephaly, is incompatible with life. The diagnosis of NTDs is often established during pregnancy via ultrasound and detection of elevated alpha-fetoprotein levels in the maternal serum or amniotic fluid. Treatment involves prophylactic administration of antibiotics and rapid surgical closure of the defect to avoid CNS infections. Supplementation with folate is an important preventative measure and should ideally be initiated 4 weeks prior to conception.

Definitiontoggle arrow icon

Epidemiologytoggle arrow icon

Epidemiological data refers to the US, unless otherwise specified.

Etiologytoggle arrow icon

Most NTDs are isolated malformations with multifactorial etiology.

Overviewtoggle arrow icon

Spinal defects (subtypes of spina bifida) [4]
Condition Description Clinical features


Closed spinal dysraphism
Spina bifida occulta
  • Most commonly affects the lower lumbar or sacral region
  • Often asymptomatic (may be an incidental finding in imaging)
  • Possible symptoms at the level of the vertebral defect:
    • Lumbar skin dimple
    • Collection of fat
    • Patch of hair
  • Often asymptomatic
  • Subcutaneous mass in the lumbar or sacral region
  • Possibly skin dimple and/or patch of hair
Open spinal dysraphism
Myeloschisis (rachischisis)
  • Portions of the neural tube completely fail to fuse, leading to bare, exposed neural tissue without coverage of meninges, bones, or skin.
  • Most severe subtype
  • Parts of the spinal cord (without meningeal coverage) herniate through the vertebral bone defect.

Cranial defects [4]
Condition Description Clinical features Diagnosis
  • Brain tissue herniates through occipital or frontal bone defect.
  • Usually covered by skin
  • Malformations and neurological deficits that vary in severity
  • Lethal in severe cases
  • Normal AFP (usually not elevated)
  • Incompatible with life

The most common NTDs are spina bifida and anencephaly.

Diagnosticstoggle arrow icon

Prenatal period [1]

AFP is only elevated in open NTDs.

Postnatal period [1]

Differential diagnosestoggle arrow icon

Tethered cord syndrome [5][6]

Congenital dermal sinus

The differential diagnoses listed here are not exhaustive.

Treatmenttoggle arrow icon

Preventiontoggle arrow icon

Supplementation of 400–800 μg of folate per day is recommended for all women who are planning for pregnancy.

Referencestoggle arrow icon

  1. Sahni M, Ohri A. Meningomyelocele. StatPearls. 2020.
  2. Congenital anomalies. Updated: September 7, 2016. Accessed: January 14, 2020.
  3. Bibbins-Domingo et al. Folic Acid Supplementation for the Prevention of Neural Tube Defects. JAMA. 2017; 317 (2): p.183-189.doi: 10.1001/jama.2016.19438 . | Open in Read by QxMD
  4. Tethered Cord Syndrome. Updated: January 1, 2010. Accessed: March 1, 2018.
  5. Tethered Spinal Cord Syndrome. . Accessed: January 17, 2020.
  6. Tolcher M, Shazly S, Shamshirsaz A, et al. Neurological outcomes by mode of delivery for fetuses with open neural tube defects: a systematic review and meta-analysis. BJOG. 2018; 126 (3): p.322-327.doi: 10.1111/1471-0528.15342 . | Open in Read by QxMD
  7. Benjamin RH, Lopez A, Mitchell LE, et al. Mortality by mode of delivery among infants with spina bifida in Texas. Birth Defects Res. 2019; 111 (19): p.1543-1550.doi: 10.1002/bdr2.1608 . | Open in Read by QxMD
  8. Recommendations: Women & Folic Acid. Updated: August 13, 2019. Accessed: January 17, 2020.
  9. Neural Tube Defects. Updated: March 1, 2012. Accessed: March 1, 2018.
  10. Spina bifida. Updated: August 27, 2014. Accessed: February 17, 2017.
  11. Dukhovny S, Wilkins-Haug L. Open Neural Tube Defects: Risk Factors, Prenatal Screening and Diagnosis, and Pregnancy Management. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: August 29, 2017. Accessed: October 10, 2017.

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