Neural Tube Defects
Neural tube defects (NTDs) are congenital anomalies caused by errors in the closure of the neural tube during early embryonic development. The most common types are spina bifida, anencephaly and encephalocele. Folic acid supplementation markedly reduces the risk.
마지막 업데이트: 2026-06-07
Definition
The neural tube is the precursor of the brain and spinal cord and closes around the 3rd-4th week of embryonic development. Neural tube defects develop when this closure fails at any stage. Failure at the head (cranial) end produces anencephaly or encephalocele, while failure at the tail (caudal) end produces spina bifida.
Types
Spina bifida is the most common NTD at the level of the spine and spinal cord, ranging from a mild (occulta) form to severe myelomeningocele in which the cord and membranes protrude. Anencephaly is a severe form in which the brain and skull largely fail to develop and is incompatible with life. In encephalocele, brain tissue and membranes protrude through a defect in the skull bone; the course depends on the amount and location of the herniated brain tissue.
Risk Factors
NTDs have a multifactorial origin. The most important and preventable risk factor is folic acid deficiency before and in early pregnancy. Other factors include a family history of NTDs, poorly controlled maternal diabetes, obesity, conditions such as high fever, and the use of certain medications (notably some antiepileptics such as valproic acid and carbamazepine, retinoids and methotrexate). Geographic and ethnic differences have also been reported.
Symptoms
Symptoms depend on the type and level. Myelomeningocele presents at birth with an open back defect and, according to the level of the lesion, leg weakness, sensory loss and bladder-bowel dysfunction; hydrocephalus and a Chiari II malformation frequently accompany it. Spina bifida occulta is usually asymptomatic but may show skin findings over the back (a hair tuft, hemangioma or dimple) or progressive symptoms due to tethered cord. Anencephaly is recognized before birth and is incompatible with life.
Diagnosis and Prevention
Prenatal screening uses elevated maternal serum alpha-fetoprotein, detailed ultrasonography (spinal defect, the 'lemon' and 'banana' signs, ventricular enlargement) and, when needed, amniocentesis; fetal MRI assesses associated anomalies. Anencephaly is usually detected on late first-trimester ultrasound. The most effective preventive measure is folic acid supplementation; use before and in the first weeks of pregnancy markedly reduces the risk of NTDs, and a higher dose is recommended for high-risk women.
Treatment and Course
Treatment varies by type. Myelomeningocele is closed surgically in selected cases in utero (fetal surgery) or soon after birth; a shunt is placed when hydrocephalus develops, and long-term multidisciplinary care involving neurosurgery, urology, orthopedics and physical therapy is required. Encephalocele is treated with early surgical repair. Anencephaly is managed with supportive care. The course differs markedly with the type, the level of the lesion and associated anomalies, and no outcome can be guaranteed.
참고 문헌
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:308-312.
- Adzick NS, Thom EA, Spong CY, et al. A randomized trial of prenatal versus postnatal repair of myelomeningocele (MOMS). N Engl J Med. 2011;364(11):993-1004.
- Copp AJ, Stanier P, Greene NDE. Neural tube defects: recent advances, unsolved questions, and controversies. Lancet Neurol. 2013;12(8):799-810.
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