What is spina bifida? |

Causes and Symptoms

The development of the fetal nervous system is the most complicated process during pregnancy. It starts a few weeks after conception and continues until well after birth. The earliest steps are the most crucial, because the basic plan of the nervous system must be established accurately if it is to work properly later.

The central nervous system begins with the formation of a thickened layer of tissue, called the neural plate, along the back of the embryo. The edges of this plate curl up to form ridges, and the whole plate rolls up into a slender tube running from the head to the rump. This cylinder is then covered over by tissues that will form the surface of the back. The front end of this tube will soon expand to become the brain, and the rest of the tube will form the spinal cord. In order for these processes to proceed properly, the tube must seal itself along its entire length. If there are any gaps where the tube does not close, it will leak and will not be able to expand and develop properly. Without such expansion, all the later stages of nervous system development will also be prevented from occurring properly.

If the neural tube fails to seal, a small opening called a neuropore will remain at some point along its length. Depending on where the opening is, a variety of abnormalities can result. When the posterior region of the neural tube fails to close, the result is spina bifida. This flaw in the neural tube in turn affects the assembly of the muscle, bone, and skin in this region. In spina bifida, which means “divided spine,” the vertebrae of the backbone do not join together properly.

The severity of spina bifida depends on how much damage has been done to the lower spinal cord region. In its mildest form, the only evidence of a problem may be that two of the bones in the spine fail to form quite right. If several vertebrae are involved, the membranes that protect the surface of the spinal cord can bulge outward, forming a ball-like mass in this region. The problems that result depend on how much of the spinal membrane is involved in this bulge. In the most severe cases, the vertebrae fail to protect the spinal cord, so that the nervous tissue itself is also involved and an opening to the outside remains at the base of the spinal cord. Additional problems with nervous system development may result, including improper fluid balances in the brain (hydrocephalus).

Because the brain and spinal column fail to develop properly in spina bifida, a variety of mental, behavioral, and physical symptoms can result. The nerve connections at the base of the spine are likely to be affected, resulting in paralysis in the lower back and legs, problems with bladder and bowel function, and loss of sensation. Because the development of the brain can also be affected, mental abilities may be impaired.

Treatment and Therapy

Effective measures have been developed to minimize the effects of spina bifida. Often, surgery is performed within twenty-four to forty-eight hours of birth to close any opening in the child’s lower back and to reconstruct the spine and other tissues in this area. Problems with feet and legs may also be dealt with surgically. If the child has symptoms of hydrocephalus, the excess fluid will be drained. Bladder and bowel function will be regulated, such as by catheterization. Eventually, prosthetic devices may be fitted to assist the child’s movement. Mental health and physical therapy experts will also be involved to assist in overcoming learning hurdles, monitoring physical development and training, and making emotional adjustments.

Perspective and Prospects

Spina bifida has been known since ancient times, but little could be done then to ease the mental and physical damage that it causes. By the 1960s, surgical procedures were being developed that could repair the damage to the spinal cord and other parts of the lower back. Improvements in physical therapy methods, as well as improved prosthetic devices, also began to make physical activity a realistic prospect for these children.

Late in the twentieth century, new insights were gained into the causes of spina bifida. The mutated genes involved were identified, and it was learned why they do not work properly. Studies of neural tube defects in mice revealed how these defects occur and how best to prevent them.

It is now known that the diet of a pregnant woman can influence neural tube development. One of the most effective measures for preventing spina bifida has been shown to be the daily intake of folic acid. Recommended doses vary from 0.4 to 4.0 mg per day based on risk status, such as prior delivery of a baby with neural tube defects. Preconceptual counseling includes recommendations for prenatal vitamins (which contain significantly more folic acid than other multivitamins) to be taken even before pregnancy. In 2000, it was reported that a folic acid supplement program for pregnant women that took place over a six-year period in South Carolina cut in half the rate of neural tube defects, including spina bifida. Doctors now know that folic acid supplements starting at the point of conception can decrease the risk of spina bifida by as much as 75 percent.

For fetuses that develop spina bifida, fetal surgery, which occurs while the fetus is in the womb, has become an option for parents. Fetal surgery can improve brain malformations, making it unnecessary for many babies to need lifelong shunts—devices that allow drainage of fluid that has accumulated around the brain. Even with the demonstrated benefits of the surgery, however, there is no guarantee that the surgery can correct all neurological functions or that it will be successful for all babies. In fact, it has been shown that fetal surgery increases the risk of a baby being born prematurely, which poses a whole new set of problems.

Support organizations for families can help them cope with the challenges of caring for children with spina bifida. Physical therapy, counseling, and various group activities are available. Thanks to improved treatment and support, it is now possible for children with this condition to lead long and healthy lives.

Bibliography

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