Myelomeningocele

Definition

Myelomeningocele is a birth defect in which the backbone and spinal canal do not close before birth. The condition is a type of spina bifida.

Alternative Names

Spina bifida; Cleft spine

Causes

Normally, during the first month of a pregnancy, the two sides of the spine (or backbone) join together to cover the spinal cord, spinal nerves and meninges (the tissues covering the spinal cord). Spina bifida refers to any birth defect involving incomplete closure of the spine.

Myelomeningocele is the most common type of spina bifida. It is a neural tube defect in which the bones of the spine do not completely form, resulting in an incomplete spinal canal. This causes the spinal cord and meninges (the tissues covering the spinal cord) to stick out of the child's back.

Myelomeningocele may affect as many as 1 out of every 800 infants.

The rest of spina bifida cases are most commonly:

• Spina bifida occulta, a condition in which the bones of the spine do not close but the spinal cord and meninges remain in place and skin usually covers the defect
• Meningoceles, a condition where the tissue covering the spinal cord sticks out of the spinal defect but the spinal cord remains in place.

Other congenital disorders or birth defects may also be present in a child with myelomeningocele. Hydrocephalus may affect as many as 90% of children with myelomeningocele. Other disorders of the spinal cord or musculoskeletal system may be seen, including syringomyelia and hip dislocation.

The cause of myelomeningocele is unknown. However, low levels of folic acid in a woman's body before and during early pregnancy is thought to play a part in this type of birth defect. The vitamin folic acid (or folate) is important for brain and spinal cord development.

Also, if a child is born with myelomeningocele, future children in that family have a higher risk than the general population. However, in many cases, there is no family connection.

Some theorize that a virus make play a role, since there is a higher rate of this condition in children born in the early winter months. Research also indicates possible environmental factors such as radiation.

Symptoms

A newborn may have a sac sticking out of the mid to lower back. The doctor cannot see through the sac when shining a light behind it. Symptoms include:

• Loss of bladder or bowel control
• Partial or complete lack of sensation
• Partial or complete paralysis of the legs
• Weakness of the hips, legs, or feet of a newborn

Other symptoms may include:

• Abnormal feet or legs, such as clubfoot
• Build up of fluid inside the skull (hydrocephalus)
• Hair at the back part of the pelvis called the sacral area
• Dimpling of the sacral area

Exams and Tests

Prenatal screening can help diagnose this condition. During the second trimester, pregnant women can have a blood test called the quadruple screen. This test screens for myelomeningocele, Down syndrome, and other congenital diseases in the baby. Most women carrying a baby with spina bifida will have a higher-than-normal levels of a protein called maternal alpha fetoprotein (AFP).

If the quadruple screen test is positive, further testing is needed to confirm the diagnosis. Such tests may include:

• Pregnancy ultrasound
• Amniocentesis

Myelomeningocele can be seen after the child is born. A neurologic examination may show that the child has loss of nerve-related functions below the defect. For example, watching how the infant responds to pinpricks at various locations may reveal where he or she can feel the sensations.

Tests done on the baby after birth may include x-rays, ultrasound, CT, or MRI of the spinal area.

Treatment

Genetic counseling may be recommended. In some cases where severe defect is detected early in the pregnancy, a therapeutic abortion may be considered.

After birth, surgery to repair the defect is usually recommended at an early age. Before surgery, the infant must be handled carefully to reduce damage to the exposed spinal cord. This may include special care and positioning, protective devices, and changes in the methods of handling, feeding, and bathing.

Children who also have hydrocephalus may need a ventricular peritoneal shunt placed. This will help drain the extra fluid.

Antibiotics may be used to treat or prevent infections such as meningitis or urinary tract infections.

Most children will require lifelong treatment for problems that result from damage to the spinal cord and spinal nerves. This includes:

• Gentle downward pressure over the bladder may help drain the bladder. In severe cases, drainage tubes, called catheters, may be needed. Bowel training programs and a high fiber diet may improve bowel function.
• Orthopedic or physical therapy may be needed to treat musculoskeletal symptoms. Braces may be needed for muscle and joint problems.
• Neurological losses are treated according to the type and severity of function loss.

Follow-up examinations generally continue throughout the child's life. These are done to check the child's developmental level and to treat any intellectual, neurological, or physical problems.

Visiting nurses, social services, support groups, and local agencies can provide emotional support and assist with the care of a child with a myelomeningocele who has significant problems or limitations.

Support Groups

See: Spina bifida resources

Outlook (Prognosis)

A myelomeningocele can usually be surgically corrected. With treatment, length of life is not severely affected. Neurological damage is often irreversible.

New problems within the spinal cord can develop later in life, especially after the child begins growing rapidly during puberty. This can lead to more loss of function as well as orthopedic problems such as scoliosis, foot or ankle deformities, dislocated hips, and joint tightness or contractures.

Many patients with myelomeningocele primarily use a wheelchair.

Possible Complications

• Difficult delivery with problems resulting from a traumatic birth, including cerebral palsy and decreased oxygen to the brain
• Frequent urinary tract infections
• Hydrocephalus
• Loss of bowel or bladder control
• Meningitis
• Permanent weakness or paralysis of legs

This list may not be all inclusive.

When to Contact a Medical Professional

Call your health care provider if:

• A sac sticks out of the spine of a newborn infant.
• The child is late in walking or crawling
• Symptoms of hydrocephalus develop, including bulging soft spot, irritability, extreme sleepiness, and feeding difficulties
• Symptoms of menigitis develop, including fever, stiff neck, irritability, and a high-pitched cry

Prevention

Folic acid supplements may help reduce the risk of neural tube defects such as myelomeningocele. It is recommended that any woman considering becoming pregnant take 0.4 mg of folic acid a day. Pregnant women need 1 mg per day.

It is important to remember that folic acid deficiencies must be corrected before becoming pregnant as the defects develop very early.

Prospective mothers may be screened to determine the amount of folic acid in their blood.

References

Kinsman SL, Johnston MV. Congenital anomalies of the central nervous system. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 592.

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