Description

• 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

Pediatric Considerations
Congenital defect

Pregnancy Considerations
Ultrasound is the primary diagnostic measure during pregnancy. Prenatal MRI is increasingly used.

Epidemiology

• Predominant age: congenital anomaly, apparent at birth
• Predominant gender: male = female

Incidence

• 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. Leakage of cerebrospinal fluid through the meningomyelocele leads to the development of hydrocephalus and brainstem herniation.

Genetics

• 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 (1).
• A woman who has delivered a child with meningomyelocele has a 2.5% risk of recurrence with subsequent pregnancies.

Risk Factors

• Maternal diabetes, antiepileptic medication use, obesity, and use of folic acid antagonists (methotrexate) may increase risk of neural tube defects; maternal age (>40 or <19 years)
• African ancestry
• Paternal occupational exposure to pesticides (2)
• Hyperthermia during early pregnancy (2)
• 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

General Prevention

• 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.
• 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
• Hydrocephalus
• 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.
• Frequent fractures of lower extremities
• Obesity
• Hypertension
• Frequent UTIs
• High prevalence of end-stage renal disease in childhood
• Kyphosis
• Scoliosis
• Pressure ulcers