Spina Bifida

– A developmental malformation of the spine in which the posterior vertebral laminae fail to close, leaving the meninges and spinal cord exposed. There are three common types: spina bifida occulta, in which the only defect is vertebral and the meninges and spinal cord are normal; spina bifida with meningocele, in which the meninges protrude through the vertebral opening, forming a cyst filled with cerebrospinal fluid and covered with skin; and spina bifida with myelomeningocele, in which the protruding cyst also contains a portion of the spinal cord and spinal nerves and is covered by a thin membrane.

Causes and Incidence

The etiology is unclear, but the most recent hypothesis suggests a genetic predisposition involving a polygenic interaction with environmental factors such as maternal malnutrition, alcohol, organic solvents, drugs, toxins, or potato blight. This interaction precipitates a faulty closure of the neural groove on day 28 of gestation. The geographic distribution and incidence of spina bifida vary widely, but it is the most common developmental defect of the central nervous system. It occurs in approximately 1 in every 1,000 live births in the United States, but the incidence has been steadily declining in recent decades. It is more common in individuals of European descent, females, and those in poverty.

Disease Process

During the normal formative stages of the nervous system, a decided depression known as a neural groove appears on the dorsal ectoderm of the embryo at approximately 20 days of gestation. The groove deepens rapidly, spreads laterally, and then fuses dorsally to form the neural tube. Neural tube formation begins in the cervical region and advances caudally and cephalically until day 28 of gestation, when both ends of the tube seal themselves off. Spina bifida occurs when the neural tube fails to close or when a closed tube splits as a result of abnormal cerebrospinal fluid pressure.

Symptoms

Manifestations vary widely, depending on the degree and location of the spinal defect. Sensory and motor disturbances parallel one another.

Occulta
Typically asymptomatic; dimple or hair growth on the skin over the malformed vertebra; weakness in feet, bowel, or bladder sphincter possible as child grows if defect goes undetected and uncorrected

Meningocele
External cystic sac seen on spinal cord at birth; hydrocephalus possible; weakness in legs or bowel and bladder sphincters is rare if defect is surgically corrected

Myelomeningocele
At birth: round, raised, poorly epithelialized sac on spinal cord that may be bluish and may be leaking or ruptured; hydrocephalus; loss of partial or total motor and sensory control below the level of the lesion; poor anal sphincter and detrusor tone; possible rectal prolapse; constant urine dribbling or urinary retention; possible joint deformities and kyphosis formed in utero Developing in childhood: clubfeet, contractures in ankles, knees, and hips; hip dislocations; scoliosis; decreasing ability to ambulate; incontinence; urinary tract infections (UTIs); constipation; skin breakdown; obesity

Potential Complications

An immediate complication often seen after birth with a leaking or ruptured sac is meningitis. Other immediate complications include hypoxia and hemorrhage. Other congenital abnormalities such as cardiac or gastrointestinal malformations may also be present. Long-term complications are associated with motor and sensory disability and include respiratory infection and failure, renal infection and failure, permanent skeletal deformities, and decubiti. In the 1950s most individuals with myelomeningocele died in infancy. Now, most have a normal life expectancy with careful and consistent health care.

Diagnostic Tests

Clinical evaluation
Pigmented spots, hairy patches, and spinal sinuses seen at birth may indicate spina bifida occulta; motor and sensory function tests determine level of injury in myelomeningocele; palpation of fontanelles and increasing head circumference indicate hydrocephalus

Ultrasound/computed tomography/magnetic resonance imaging
Abnormalities of head or spine or both

Myelography
Spinal defects

Intravenous pyelography
Abnormalities in renal system

Urodynamics
To assess detrusor and sphincter function

Fetal ultrasonography
May detect major myelomeningocele defects

Alpha-fetoprotein
Elevated at 16 to 18 weeks’ gestation

Treatments

Surgery
Repair and closure of defect within 24 to 72 hours after birth; ventriculoperitoneal shunt to treat hydrocephalus; shunt revisions as child ages or if shunt is not patent or functional; corrective orthopedic procedures for contractures, clubfeet, scoliosis (spinal instrumentation), hip dislocations; vesicostomy for vesicourethral reflux; augmentation enterocystoplasty to increase bladder capacity and reduce bladder pressure; placement of artificial urinary sphincter or ureteral sling to aid bladder emptying; urinary diversion to control chronic urine leakage and retention.

Drugs
Collagen injection in sphincter submucosa to control bladder incontinence; stool softeners and laxatives for constipation; antispasmodics to treat bladder spasms; antiinfective drugs for UTI.

General
Initial care: monitoring for associated defects and complications; measures to prevent infections; monitoring of patency and functioning of ventriculoperitoneal shunt; adequate hydration and nutrition; normal infant stimulation; meticulous skin care; proper positioning and body alignment; monitoring of intake and output; emotional support of family; teaching parents to hold, feed, and stimulate infant and any special techniques needed for care; physical therapy and range-of-motion (ROM) exercises; safety measures for decreased sensation Long term: consistent medical monitoring by neurologists/ neurosurgeons for shunt function and revision and spinal cord tethering; orthopedic surgeons for treatment of contractures, gait analysis, and bracing; urologists for bladder and kidney function; pediatricians for minor infections, bowel program and coordination; physical therapists for maintenance of ROM, prevention of contractures, gait training, strengthening, and endurance; occupational therapists for activities of daily living; intermittent catheterization for bladder control; weight-maintenance diet to prevent obesity and maintain ambulation; counseling for long-term adaptation; case management for long-term support and education of individual, family, and school and coordination of ongoing care.