Spina Bifida (Myelomeningocele)
Spina bifida is a congenital defect of the spine and spinal cord caused by incomplete closure of the neural tube during embryonic development. In its most severe form, myelomeningocele, the spinal cord and its membranes protrude through the spinal column. Folic acid supplementation markedly reduces the risk, and with modern multidisciplinary care many patients lead independent lives.
最后更新: 2026-06-07
Definition
Spina bifida (Latin for 'split spine') is the most common neural tube defect. Around the 3rd-4th week of embryonic development, failure of the neural tube to close completely affects the spine and the underlying spinal cord. Myelomeningocele (MMC) is the most severe form, in which the spinal cord, nerve roots and membranes (meninges) protrude through the spinal column without skin cover.
Types
Spina bifida occulta is the mildest form, with only a bony defect of the spine; the spinal cord is usually normal and most cases are asymptomatic. In meningocele, only the membranes and cerebrospinal fluid protrude while the cord stays within the canal, and neurological involvement is generally mild. Myelomeningocele is the most common and most severe form, with the spinal cord and nerve roots exposed, causing motor and sensory loss and bladder-bowel dysfunction.
Causes and Risk Factors
Spina bifida has a multifactorial (genetic and environmental) origin. The most important and preventable risk factor is folic acid deficiency before and in early pregnancy. Other factors include a family history of neural tube defects, poorly controlled maternal diabetes, obesity and the use of certain medications (notably some antiepileptics such as valproic acid). Folic acid supplementation before and in the first weeks of pregnancy substantially lowers the risk.
Associated Conditions
Myelomeningocele is frequently accompanied by a Chiari II malformation, in which cerebellar and brainstem structures are displaced below the foramen magnum, disturbing cerebrospinal fluid flow and leading to hydrocephalus in a large proportion of cases. Tethered cord, scoliosis, hip dislocation and foot deformities (such as talipes equinovarus) may also occur. Bladder and bowel dysfunction (neurogenic bladder) is present in most cases.
Diagnosis
Diagnosis is made before and after birth. 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 adds detail. After birth the back defect is recognized on inspection; cranial and spinal MRI assess the level of the defect, Chiari II, hydrocephalus and tethered cord. Renal ultrasound and urodynamic studies evaluate bladder function.
Treatment
Treatment requires a multidisciplinary approach. In selected cases the defect is closed in utero during mid-pregnancy (fetal surgery), or more commonly soon after birth (usually within the first 24-72 hours); early closure reduces the risk of infection. When hydrocephalus develops, a ventriculoperitoneal shunt or, in selected cases, endoscopic third ventriculostomy is used. Long-term care combines neurosurgery, urology (including clean intermittent catheterization), orthopedics, physical therapy and developmental support.
Course
The course depends on the level of the defect, associated anomalies and the quality of care; lower (lumbosacral) lesions carry a higher chance of walking and independence, while higher lesions more often require assistive devices. With modern care many patients attend school, work and live independently. Outcomes vary markedly between patients and none can be guaranteed; regular multidisciplinary follow-up is essential.
参考文献
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:280-287.
- 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.
- Bowman RM, McLone DG, Grant JA, Tomita T, Ito JA. Spina bifida outcome: a 25-year prospective. Pediatr Neurosurg. 2001;34(3):114-120.
本文仅供一般参考，不能替代医疗检查。诊断与治疗决策因人而异。