Myelomeningocele is a congenital disorder (birth defect) where the backbone and spinal canal do not close before birth. This can result in the spinal cord and its covering membranes to protrude out of the infant’s back.
Causes, incidence, and risk factors
Myelomeningocele is one of the most common birth defects of the central nervous system. It is a neural tube defect in which the bones of the spine do not completely form, and the spinal canal is incomplete. This allows the spinal cord and meninges (the membranes covering the spinal cord) to protrude out of the child’s back.
Spina bifida includes any congenital defect involving insufficient closure of the spine. Myelomeningocele accounts for about 75% of all cases of spina bifida and may affect as many as 1 out of every 800 infants. The rest of the cases are most commonly spina bifida occulta (where the bones of the spine do not close, the spinal cord and meninges remain in place, and skin usually covers the defect) and meningoceles (where the meninges protrude through the vertebral defect but the spinal cord remains in place).
The cause of myelomeningocele is unknown. However, Folic acid deficiency is thought to play a part in neural tube defects. The disorder appears to be more common in families. If a child is born with myelomeningocele, subsequent children in that family have a higher risk than the general population.
A viral cause or trigger has been theorized because there is a higher incidence of the defect in children born in the early winter months. Research also indicates possible environmental factors such as radiation.
Protrusion of the spinal cord and meninges damages the spinal cord and nerve roots, causing a decrease or lack of function of body areas controlled at or below the defect. Symptoms are related to the anatomic level of the defect. Most defects occur in the lower lumbar or sacral areas of the back (the lowest areas of the back) because this area is normally the last part of the spine to close.
Symptoms include partial or complete paralysis of the legs, with partial or complete lack of sensation, and may include loss of bladder or bowel control. The exposed spinal cord is susceptible to infection (Meningitis).
Other congenital disorders may also be present in the child, usually disorders of the spinal cord or the musculoskeletal system such as hydrocephalus (which may affect as many as 90% of children with myelomeningocele), syringomyelia, hip dislocation, or similar disorders.
- visible sac-like protrusion on the mid to lower back of a newborn o not translucent when a light is shone from behind the sac
- weakness of the hips, legs, or feet of a newborn
Spina bifida occulta may be indicated by:
- a tuft of hair at the sacral area (back part of the pelvis)
- dimpling of the sacrum
Signs and tests
Myelomeningocele is a visible defect after the child is born. Neurologic examination may indicate loss of neurologic functions below the defect. For example, response of the infant to pinpricks at various locations may indicate the level where sensation is maintained.
During the first trimester, pregnant women can have a blood test called a triple screen. This test screens for spina bifida, Down syndrome, and other congenital diseases in the baby. Eighty-five percent of women carrying a fetus with spina bifida will show elevated maternal serum alpha fetoprotein (one of the three proteins measured in this blood test).
The triple screen has a high false positive rate, so if it is positive further testing is required to confirm the diagnosis. A prenatal ultrasound is then done and is usually a reliable test for spina bifida. Occasionally amniocentesis (test of the amniotic fluid) is done.
- Spine X-rays may reveal the exact extent and location of the defect.
- Spine ultrasound may show an abnormal spinal cord or spine.
- Spine CT or spine MRI scan are occasionally used to determine the location and extent of the defect.
The goals of initial treatment are to reduce the amount of neurologic damage caused by the defect, to minimize complications such as infection, and to aid the family in coping with the disorder. Follow-up neurologic testing as the child gets older helps to guide rehabilitation.
Early surgical repair of the defect is usually recommended, although surgical repair may be performed later to allow the infant to tolerate the procedure better. Currently there are centers attempting experimental in utero surgical repair of spina bifida (surgical repair of the defect while the fetus is still developing in the uterus).
Before surgery, the infant must be handled carefully to reduce damage to the exposed spinal cord. This may include positioning, protective devices, and modifications in the methods of handling, feeding, bathing, and caring for the infant.
Gentle downward pressure over the bladder may aid in drainage of the bladder. In severe cases, indwelling or intermittent bladder drainage catheters may be needed. A diet high in fiber, and bowel training programs, may improve bowel function. Orthopedic intervention or physical therapy may be needed to treat musculoskeletal symptoms. Other neurologic losses are treated according to the type and extent of the loss of function. The goal of these interventions is to minimize future disability and maximize functioning.
Occasionally, surgical shunting to correct hydrocephalus causes the myelomeningocele to spontaneously reduce, and normal growth of the child may cover the defect.
Counseling and support groups (such as the spina bifida - support group) may help families to cope with the disorder.
Genetic counseling may be recommended. In some cases where severe defect is detected early in the pregnancy, therapeutic Abortion (Termination Of Pregnancy) may be considered.
Spina Bifida Association of America
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The defect of myelomeningocele can usually be surgically corrected. With treatment, length of life is not severely affected. Neurologic damage is often irreversible.
- difficult delivery with problems subsequent to traumatic birth (including Cerebral palsy and decreased oxygen to the brain)
- permanent disability, with weakness or paralysis of legs
- loss of bowel or bladder control
- frequent Urinary tract infections
- coexisting defects (hydrocephalus or other defects)
Calling your health care provider
Call your health care provider if a protrusion is present on the spine of a newborn infant.
Call for an appointment with your health care provider if the child is late in walking or crawling.
Follow-up monitoring should be ongoing as the child ages to assess extent of neurologic damage, symptoms of complications occur. Symptoms of hydrocephalus include bulging soft spots (fontanelles), irritability, Lethargy, and difficulty feeding. Symptoms of Meningitis include fever, stiff neck (unwillingness to bend or move neck/head), irritability, and a high-pitched cry.
Folic acid supplements may be effective at reducing the risk of neural tube defects such as myelomeningocele. Folic acid (folate) deficiencies must be corrected BEFORE becoming pregnant as the defects develop very early. Prospective mothers may be screened to determine their serum folate level. It is recommended that any woman considering becoming pregnant take 0.4mg of Folic acid a day. Pregnant women need 1 mg per day.
by Sharon M. Smith, M.D.