Spina bifida is defective closure of the vertebral column. Although the cause is not known, low folate levels during pregnancy increase risk. Some children are asymptomatic, and others have severe neurologic dysfunction below the lesion. Open spina bifida can be diagnosed prenatally by ultrasonography or suggested by elevated α-fetoprotein levels in maternal serum and amniotic fluid. After birth, a lesion is typically visible on the back. Treatment is usually surgical.
Spina bifida is one of the most serious neural tube defects compatible with prolonged life. This defect is one of the more common congenital anomalies overall, with an incidence in the US of about 1/1500. It is most common in the lower thoracic, lumbar, or sacral region and usually extends for 3 to 6 vertebral segments. Severity ranges from occult, in which there are no apparent anomalies, to protruding sacs (spina bifida cystica), to a completely open spine (rachischisis) with severe neurologic disability and death.
In occult spinal dysraphism (OSD), anomalies of the skin overlying the lower back (typically in the lumbosacral area) occur; these include sinus tracts that have no visible bottom, are above the lower sacral area, or are not in the midline; hyperpigmented areas; asymmetry of the gluteal cleft with the upper margin deviated to one side; and tufts of hair. These children often have anomalies in the underlying portion of the spinal cord, such as lipomas and tethering (in which the cord has an abnormal attachment—Fig. 1: Forms of spina bifida.).
In spina bifida cystica, the protruding sac can contain meninges (meningocele), spinal cord (myelocele), or both (myelomeningocele). In a myelomeningocele, the sac usually consists of meninges with a central neural plaque. If not well covered with skin, the sac can easily rupture, increasing the risk of meningitis.
Hydrocephalus is common because many children have a Chiari II type malformation (see Hydrocephalus).
Syringomyelia (a dilation of the normally small fluid-filled central canal of the spinal cord—see also Syrinx of the Spinal Cord or Brain Stem) and other congenital anomalies and soft-tissue masses around the spinal cord may be present.
Causes seem multifactorial. Folate deficiency is a significant factor, and there seems to be a genetic component. Other risk factors include maternal use of certain drugs (eg, valproate) and maternal diabetes.
Symptoms and Signs
Many children with minor defects are asymptomatic.
When the spinal cord or lumbosacral nerve roots are involved, as is usual, varying degrees of paralysis and sensory deficits are present below the lesion. Rectal tone is usually decreased.
Hydrocephalus (see Hydrocephalus) may cause minimal symptoms or signs of increased intracranial pressure. Brain stem involvement may cause manifestations such as stridor, swallowing difficulties, and intermittent apnea.
Lack of muscle innervation leads to atrophy of the legs. Because paralysis occurs in the fetus, orthopedic problems may be present at birth (eg, clubfoot, arthrogryposis of the legs, dislocated hip—see Congenital Hip, Leg, and Foot Abnormalities). Kyphosis is sometimes present and can hinder surgical closure and prevent the child from lying supine. Scoliosis may develop later and is more common among children with higher lesions (ie, above L3).
Paralysis also impairs bladder function, occasionally leading to a neurogenic bladder and, consequently, urinary reflux, which can cause hydronephrosis, frequent UTIs, and, ultimately, kidney damage.
Spinal cord imaging, with ultrasonography or MRI, is essential in children with OSD; even children with minimal cutaneous findings may have underlying spinal abnormalities (those with overt defects do not require spinal cord imaging because the anatomy is known). Plain x-rays of the spine, hips, and, if they are malformed, lower extremities are done. Cranial imaging using ultrasonography, CT, or MRI is done to look for hydrocephalus and syringomyelia.
Once the diagnosis of spina bifida is made, urinary tract evaluation is essential and includes urinalysis, urine culture, BUN and creatinine determination, and ultrasonography. Measurement of bladder capacity and pressure at which urine exits into the urethra can determine prognosis and intervention. Need for further testing, such as urodynamics and voiding cystourethrogram, depends on previous findings and associated anomalies.
Prenatal screening can be done by doing fetal ultrasonography and by measuring maternal serum levels of α-fetoprotein (see Maternal serum screening for neural tube defects), ideally between 16 wk and 18 wk gestation; levels can also be done on amniotic fluid samples if previous testing suggests an increased risk. Elevated levels suggest increased risk of spina bifida cystica (OSD rarely causes elevated levels).
Prognosis varies by the level of cord involvement and the number and severity of associated anomalies. Prognosis is worse for children with higher cord level (eg, thoracic) lesions or who have kyphosis, hydrocephalus, early hydronephrosis, and associated congenital anomalies. With proper care, however, most children do well. Loss of renal function and ventricular shunt complications are the usual causes of death in older children.
Without early surgical treatment, neurologic damage can progress in OSD. Treatment for all spina bifida requires a united effort by specialists from several disciplines; neurosurgical, urologic, orthopedic, pediatric, psychiatric/psychologic, and social service evaluations are important. It is important to assess the type, vertebral segment, and extent of the lesion; the infant's health status; and associated anomalies. Discussion with the family should ascertain the family's strengths, desires, and resources, and community resources, including availability of ongoing care.
A myelomeningoocele identified at birth is covered immediately with a sterile dressing. If the myelomeningocele is leaking CSF, antibiotics are started to prevent meningitis. Neurosurgical repair of a myelomeningocele or an open spine typically is done within the first 72 h after birth to reduce the risk of meningeal or ventricular infection. If the lesion is large or is in a difficult location, plastic surgeons may be consulted to ensure adequate closure.
Hydrocephalus may require a shunt procedure in the neonatal period; sometimes a ventricular shunt is inserted when the back is repaired (see Treatment).
Kidney function must be monitored closely, and UTI should be treated promptly. Obstructive uropathy at either the bladder outlet or ureteral level must be treated vigorously to prevent infection. When children are between 2 and 3 yr of age, or at any time if they have elevated pressure in the bladder with vesicoureteral reflux, clean intermittent catheterization is done to empty the bladder on a regular basis. Catheterization increases continence and maintains bladder and kidney health.
At around the same time, children are placed on the commode or toilet after meals to encourage fecal continence. Well-balanced diets are encouraged; stool softeners, laxatives, or a combination may be helpful to ensure regular bowel movements and to increase continence (see Treatment). In older children, an antegrade colonic enema procedure, in which a hole is placed through the abdominal wall into the colon to allow infusion of liquids, can improve continence. The hole is kept open by a tube (eg, a gastrostomy feeding tube).
Orthopedic care should begin early. If a clubfoot is present, a cast is applied; surgery is often necessary after casting (see Talipes equinovarus). Hip joints are checked for dislocation. Affected children should be monitored for development of scoliosis, pathologic fractures, pressure sores, and muscle weakness and spasm.
Folate supplementation (400 to 800 mcg po once/day) in women beginning 3 mo before conception and continuing through the 1st trimester reduces the risk of neural tube defects (see Prevention). Women who are considered at high risk of neural tube defects, ie, women who have had a fetus or infant with a neural tube defect, should take folate 4 mg (4000 mcg) po once/day.
Last full review/revision December 2014 by Stephen J. Falchek
Content last modified December 2014