Spinal cord defects
Spinal cord defects: Excerpt from Handbook of Diseases
Various malformations of the spine — including spina bifida, meningocele, and myelomeningocele — result from defective embryonic neural tube closure during the first trimester of pregnancy. Generally, these defects occur in the lumbosacral area, but they’re occasionally found in the sacral, thoracic, and cervical areas.
Spina bifida occulta is the most common and least severe spinal cord defect. It’s characterized by incomplete closure of one or more vertebrae without protrusion of the spinal cord or meninges.
However, in more severe forms of spina bifida, incomplete closure of one or more vertebrae causes protrusion of the spinal contents in an external sac or cystic lesion. In spina bifida with meningocele, this sac contains meninges and cerebrospinal fluid (CSF). In spina bifida with myelomeningocele (meningomyelocele), this sac contains meninges, CSF, and a portion of the spinal cord or nerve roots distal to the conus medullaris.
Spina bifida is relatively common and affects about 5% of the population. In the United States, about 12,000 neonates each year are born with some form of spina bifida; spina bifida with myelomeningocele is less common than spina bifida occulta and spina bifida with meningocele. Incidence is highest in persons of Welsh or Irish ancestry.
The prognosis varies with the degree of accompanying neurologic deficit. It’s worst in patients with large open lesions, neurogenic bladders (which predispose to infection and renal failure), or total paralysis of the legs.
CLINICAL TIP: The prognosis is better in patients with spina bifida occulta and meningocele than in those with myelomeningocele. Many patients with these conditions can lead normal lives.
Causes
Normally, about 20 days after conception, the embryo develops a neural groove in the dorsal ectoderm. This groove rapidly deepens, and the two edges fuse to form the neural tube.
By about day 23, this tube is completely closed except for an opening at each end. Theoretically, if the posterior portion of this neural tube fails to close by the 4th week of gestation, or if it closes but then splits open from a cause such as an abnormal increase in CSF later in the first trimester, a spinal defect results.
Viruses, radiation, and other environmental factors may be responsible for such defects. However, spinal cord defects occur more often in offspring of women who have previously had children with similar defects, so genetic factors may also be responsible.
Signs and symptoms
Indications vary depending on the type of defect.
Spina bifida occulta
Although overt signs may be absent, spina bifida occulta is often accompanied by a depression or dimple, tuft of hair, soft fatty deposits, port wine nevi, or a combination of these abnormalities on the skin over the spinal defect.
Spina bifida occulta doesn’t usually cause neurologic dysfunction but occasionally is associated with foot weakness or bowel and bladder disturbances. Such disturbances are especially likely during rapid growth phases, when the spinal cord’s ascent within the vertebral column may be impaired by its abnormal adherence to other tissues.
Meningocele and myelomeningocele
A saclike structure protrudes over the spine in both meningocele and myelo-meningocele.
Like spina bifida occulta, meningocele rarely causes neurologic deficit. But myelomeningocele, depending on the level of the defect, causes permanent neurologic dysfunction, such as flaccid or spastic paralysis and bowel and bladder incontinence.
Associated disorders include trophic skin disturbances (ulcerations, cyan-osis), clubfoot, knee contractures, and hydrocephalus (in about 90% of patients). Mental retardation, Arnold-Chiari syndrome (in which part of the brain protrudes into the spinal canal), and curvature of the spine can also occur.
Diagnosis
The diagnosis varies with the type of defect.
Spina bifida occulta
Although often overlooked, spina bifida occulta is occasionally palpable, and a spinal X-ray can show the bone defect. Myelography can differentiate it from other spinal abnormalities, especially spinal cord tumors.
Meningocele and myelomeningocele
Meningocele and myelomeningocele are obvious on examination; transillumination of the protruding sac can sometimes distinguish between them. (In meningocele, it typically transilluminates; in myelomeningocele, it doesn’t.)
In myelomeningocele, a pinprick examination of the legs and trunk shows the level of sensory and motor involvement; skull X-rays, cephalic measurements, and a computed tomography scan demonstrate associated hydrocephalus.
Other appropriate laboratory tests in patients with myelomeningocele include urinalysis, urine cultures, and tests for renal function starting in the neonatal period and continuing at regular intervals.
Although amniocentesis can detect only open defects, such as myelomeningocele and meningocele, this procedure is recommended for all pregnant women who have previously had children with spinal cord defects; these women are at an increased risk for having children with similar defects. If these defects are present, amniocentesis shows increased alpha-fetoprotein levels by 14 weeks’gestation.
Ultrasonography can also detect or confirm the presence and extent of neural tube defects.
Treatment
Spina bifida occulta usually requires no treatment. Treatment of meningocele consists of surgical closure of the protruding sac and continual assessment of growth and development.
Treatment of myelomeningocele requires repair of the sac and supportive measures to promote independence and prevent further complications. Surgery doesn’t reverse neurologic deficits. A shunt may be needed to relieve associated hydrocephalus.
If the patient has a severe spinal defect, short- and long-term treatment will require a team approach, including a neurosurgeon, orthopedist, urologist, nurse, social worker, occupational and physical therapists, and parents.
Rehabilitation
In children or adults, rehabilitation measures may include:
❑ waist supports, long leg braces, walkers, crutches, and other ortho-pedic appliances
❑ diet and bowel training to manage fecal incontinence
❑ neurogenic bladder management to reduce urinary stasis, possibly intermittent catheterization, and antispasmodics, such as bethanechol or propantheline. In severe cases, insertion of an artificial urinary sphincter is often sucsuccessful; a urinary diversion is used as a last resort to preserve kidney function.
Special considerations
Before surgery for meningocele or myelomeningocele:
❑ Prevent local infection by cleaning the defect gently with sterile saline solution or other solutions. Inspect the defect often for signs of infection, and cover it with sterile dressings moistened with sterile saline solution. Don’t use ointments on the defect; they may cause skin maceration.
❑ Prevent skin breakdown by placing sheepskin or a foam pad under the infant. Keep skin clean, and apply lotion to knees, elbows, chin, and other pressure areas. Give antibiotics as needed.
❑ Handle the infant carefully. Hold and cuddle him, but avoid placing pressure on the sac. When holding him on your lap, position him on his abdomen, and teach the parents to do the same.
❑ Usually, the infant can’t wear a diaper or a shirt until after surgical correction because it will irritate the sac, so keep him warm in an infant Isolette. Position him on his abdomen with the head of the bed slightly elevated to prevent contamination of the sac with urine or feces.
❑ Provide adequate time for parent-child bonding, if possible.
❑ Measure head circumference daily, and watch for signs of hydrocephalus and meningeal irritation, such as fever or nuchal rigidity. Be sure to mark the spot so you get accurate readings.
❑ Minimize contractures with passive range-of-motion exercises and casting. To prevent hip dislocation, abduct the hips with a pad between the knees or with sandbags and ankle rolls.
❑ Monitor intake and output. Watch for decreased skin turgor, dryness, or other signs of dehydration. Provide meticulous skin care to genitals and buttocks to prevent infection.
❑ Ensure adequate nutrition.
After surgical repair of the defect:
❑ Watch for hydrocephalus, which often follows such surgery. Measure the child’s head circumference.
❑ Monitor vital signs often. Watch for signs of shock (decreased blood pressure, tachycardia, lethargy), infection (malaise, elevated temperature, alteration in feeding pattern), and increased intracranial pressure (projectile vomiting).
❑ Frequently assess the infant’s fontanels. Remember that before age 2, infants don’t show typical signs of increased intracranial pressure because suture lines aren’t fully closed. The most telling sign is bulging fontanels.
❑ Change the dressing regularly, and watch for any signs of drainage, wound rupture, or infection.
❑ If leg casts have been applied to treat deformities, watch for signs that the child is outgrowing the cast. Check distal pulses to ensure adequate circulation. Petal the edges of the cast to prevent softening and skin irritation. Use a cool-air blow-dryer to dry skin under the cast. Periodically check for foul odor and other indications of skin breakdown.
❑ Help parents work through their feelings of guilt, anger, and helplessness.
❑ Teach parents how to cope with their infant’s problems and successfully meet long-range treatment goals. (See Discharge teaching in spinal cord defects.)
❑ Refer parents for genetic counseling, and suggest that amniocentesis be performed in future pregnancies. For more information and names of support groups, refer parents to the Spina Bifida Association of America or other similiar organizations.
❑ A high percentage of children with spina bifida have latex allergy. Teach the patient about latex allergy and to avoid products that use latex as an ingredient. Give the patient a list of such products, if available.
❑ Teach women of childbearing age to take a daily vitamin with 400 mcg folic acid to minimize the risk of neural tube defects.
Pictures
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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