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- Protrusion of nerve tissue and its covering through a defect in the vertebrae
- Caused by incomplete neural tube closure during 3 to 4 weeks’ gestation, thus exposing meninges and spinal cord
- Frequently associated with hydrocephalus, Chiari syndrome, and tethered cord syndrome
- Significantly lower cognitive development than unaffected children
- Nearly all have bladder dysfunction (i.e., neurogenic bladder)
- Significant morbidity and mortality from hindbrain herniation (Chiari II malformation) (1)
- Children with meningomyelocele do attain adulthood; consequently, developmental concerns must be addressed including driving and sexual activity.
- System(s) affected: musculoskeletal; nervous; renal/urologic; skin/exocrine
- Synonym(s): spina bifida; myelomeningocele; meningocele; lipomeningocele; spinal dysraphism; open neural tube defect
Always use latex precautions. 1/3 of spina bifida patients have latex allergy. Recommend alert identification bracelet once documented.
Ultrasound is the primary diagnostic measure during pregnancy. Prenatal MRI is increasingly used.
- Predominant age: congenital anomaly, apparent at birth
- Predominant gender: male = female
- Worldwide incidence is 1 to 10/1,000 births.
- In the United States, 1,500 new cases per year
- In the United States, 3.4/10,000 live births per year
Etiology and Pathophysiology
- Maternal folic acid deficiency is an environmental factor strongly associated with neural tube defects.
- The ultimate cause of spinal dysraphism is unclear.
- Experimental and clinical evidence suggest that the primary cause is chronic, mechanical, and amniotic fluid–induced chemical trauma, which leads to progressive damage of neural tissue during gestation (1)[C]. Leakage of cerebrospinal fluid through the meningomyelocele leads to the development of hydrocephalus and brainstem herniation.
- The majority of meningomyeloceles occurs as isolated incidents and is of multifactorial origin.
- Data support fetal karyotype testing for diagnostic testing and for counseling regarding recurrence risk.
- A large meta-analysis study suggests that the MTHFD1 G1958A gene polymorphism is related to neural tube defects (2).
- A woman who has delivered a child with meningomyelocele has a 2.5% risk of recurrence with subsequent pregnancies.
- Maternal diabetes, antiepileptic medication use, obesity, and use of folic acid antagonists (methotrexate) may increase risk of neural tube defects; maternal age (>40 or under 19 years) (3)
- African ancestry (3)
- Paternal occupational exposure to pesticides (3)
- Hyperthermia during early pregnancy (3)
- Maternal use of valproic acid and related compounds during the 1st trimester increases risk of neural tube defects.
- Previous children with spina bifida
- Insufficient maternal levels of folic acid
- Vitamin B12 deficiency
- The vital period of closure of the rostral and caudal neural pores is at 6 weeks of gestation.
- As of 2009, U.S. Preventive Services Task Force (USPSTF) advisory recommends adequate folate intake 0.4 to 0.8 mg/day by sexually active women begun at least 1 month before pregnancy and continuing through the 1st trimester (4)[A].
- Fetal surgery places both mother and fetus at risk for complications, including preterm delivery and uterine dehiscence.
- Intrauterine repair before 26 weeks’ gestation has been shown to reduce the incidence of shunt-dependent hydrocephalus and decrease hindbrain herniation but does not seem to improve age at onset of walking.
Commonly Associated Conditions
- About 10% may be associated with a genetic syndrome.
- Less commonly associated with a chromosomal abnormality such as trisomies 13 and 18
- High risk of infection at time of birth
- Chiari II malformation present in nearly all infants with meningomyelocele
- >80% of patients require ventriculoperitoneal shunting (VPS) and have ambulation impairments such that 2/3 of patients are wheelchair bound by adulthood (1).
- Frequent fractures of lower extremities
- Frequent UTIs
- High prevalence of end-stage renal disease in childhood
- Pressure ulcers