What do doctors call these conditions?
Spina bifida, meningocele, myelomeningocele
What are these conditions?
Defective neural tube closure in the embryo during the first trimester of pregnancy causes various spinal malformations. Generally, these defects occur in the lumbosacral area, but they are occasionally found in the sacral, thoracic, and cervical areas.
Spina bifida occulta is the most common and least severe spinal cord defect. Although one or more vertebrae fail to close completely, the spinal cord or meninges (membranes covering the brain and spinal cord) do not protrude.
However, in more severe forms of spina bifida, incomplete closure of one or more vertebrae causes the spinal contents to protrude and form an external sac or cystic lesion. In spina bifida with meningocele, this sac contains meninges and cerebrospinal fluid. In spina bifida with myelomeningocele, this sac contains meninges, cerebrospinal fluid, and a portion of the spinal cord or nerve roots distal to the conus medullaris.
Spina bifida is relatively common, affecting about 5% of the population. In the United States, approximately 12,000 infants each year are born with some form of spina bifida.
The prognosis varies with the degree of accompanying neurologic deficit. It’s worst in people with large open lesions, neurogenic bladders (which predispose to infection and kidney failure), or total paralysis of the legs. Because such features are usually absent in spina bifida occulta and meningocele, the prognosis is much better than in myelomeningocele, and many people with these conditions can lead normal lives.
What causes them?
Normally, about 20 days after conception, the embryo develops a neural groove in the dorsal area. This groove rapidly deepens, and the two edges come together to form the neural tube. By about day 23, this tube is completely closed except for an opening at each end. If the posterior portion of the neural tube fails to close by the fourth week of pregnancy, or if it closes but then splits open from a cause such as an abnormal increase in cerebrospinal fluid later in the first trimester, a spinal defect is likely to result.
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 contribute.
What are their symptoms?
Spina bifida occulta is often accompanied by skin abnormalitiessuch as a depression or dimple, tuft of hair, soft fatty deposits, port-wine nevi (skin discoloration), or a combination of these -located over the spinal defect; however, such signs may be absent. 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.
In both meningocele and myelomeningocele, a saclike structure protrudes over the spine. Like spina bifida occulta, meningocele rarely causes neurologic deficits. But myelomeningocele, depending on the level of the defect, causes permanent neurologic dysfUnction, such as flaccid or spastic paralysis and bowel and bladder incontinence.
How are they diagnosed?
Spina bifida occulta is often overlooked, although it’s occasionally palpable and spinal X-ray can show the bone defect. Myelography can differentiate it from other spinal abnormalities, especially spinal cord tumors.
Meningocele and myelomeningocele are obvious on examination; backlighting the protruding sac can sometimes distinguish between them. (Light typically passes through a meningocele, but not through a myelomeningocele.) In myelomeningocele, a pinprick exam of the legs and trunk shows the level of sensory and motor involvement; skull X-rays, skull measurements, and computed tomography scan (commonly called a CAT scan) demonstrate associated fluid in the brain. Other appropriate lab tests in people with myelomeningocele include urinalysis, urine cultures, and tests for kidney function – starting in the neonatal period and continuing at regular intervals.
Although amniocentesis can detect only open spinal defects, this procedure is recommended for all pregnant women who have previously had children with spinal cord defects because there is a greater risk of having another child with similar defects. If these defects are present in the fetus, amniocentesis shows increased alpha-fetoprotein levels by the 14th week of pregnancy. Ultrasonography can also detect or confirm the presence and extent of neural tube defects.
How are they treated?
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 inserted to relieve associated fluid in the brain.
Rehabilitation measures may include waist supports, long leg braces, walkers, crutches, and other orthopedic appliances; diet and bowel training to manage fecal incontinence; neurogenic bladder management to reduce urinary stasis; possibly intermittent catheterization; and antispasmodics such as Urecholine or Pro-Banthine. In severe cases, insertion of an artificial urinary sphincter is often successful; urinary diversion is used as a last resort to preserve kidney function.
