What is spina bifida?
Spina bifida is the incomplete closure of the spinal column during fetal development. It is a type of neural tube birth defect that scientists believe is caused by a combination of genetic and environmental factors, though they do not know the exact cause. Women who take vitamin supplements containing folic acid during pregnancy are much less likely to have children born with this condition. The defect is occurs in about one in every 1,000 births in the United States.
During normal development, the edges of a plate of cells curl toward one another, forming the tube that will later become the brain and spinal cord. If the neural tube does not close properly, spina bifida can be one of the defects that result. It can affect the brain, spinal cord and/or the meninges (the protective covering around the brain and spinal cord).
There are three forms of spina bifida, including:
- Occulta, often called the 'hidden' form, is the mildest and most common kind of spina bifida. One or more vertebrae may have small gaps where the bone failed to form the typical ring-like structure. This form rarely causes symptoms or disability because the spinal cord is intact.
- Meningocele is the rarest form of spina bifida. It is characterized by protruding of the membrane that surrounds the spinal cord through an opening in the spinal column. Usually, there are no symptoms, but urinary and bowel dysfunction can develop over time, so children with this form must be closely monitored.
- Myelomenigocele, the severest form of spina bifida, occurs when the meninges (the protective covering of the spinal cord) and spinal nerves come through the open part of the bony spine. It causes irreversible nerve damage and severe disabilities. It can also cause hydrocephalus, or water on the brain, in 70 to 90 percent of those children who have it. That's because cerebral spinal fluid, which normally protects the brain and spinal cord, cannot drain properly due to the defect. This leads to enlargement of the head and, without treatment, may result in mental retardation. (Hydrocephalus also occurs in children without spina bifida.)
How is spina bifida diagnosed?
Spina bifida is usually diagnosed with a blood test during pregnancy. The test is given during the second trimester and screens for normal levels of maternal serum alpha fetoprotein (MSAFP). A small amount of this protein crosses the placenta and winds up in the mother's blood. If the levels are too high, it may be an indication of a neural tube defect. Additional tests, however, are needed to confirm a case of spina bifida. These may include ultrasound or amniocentesis. Mild cases that go undetected during pregnancy may be discovered as part of routine exams or during X-ray exams for unrelated conditions. The mildest cases likely remain unnoticed.
How is spina bifida treated?
There is no cure for spina bifida. Once nerves have been damaged or lost, they cannot be repaired or replaced. Treatment depends on the type and severity of the form of spina bifida. Children with the mildest forms may not need any treatment, or may require surgery as they grow.
Children with the most severe form, myelomeningocele, often undergo surgery within 24 hours of birth to close the defect and prevent infection and further damage to exposed nerves. Meningocele spina bifida can also be repaired surgically.
Fetal or prenatal surgery can also offer hope of correcting or minimizing a variety of life-threatening or potentially disabling conditions affecting the fetus, helping to facilitate a safe delivery while protecting the health of the mother. Open fetal surgery, which operates on mother and fetus via an open incision on both, is used before birth for spina bifida at the UC Davis Fetal Care and Treatment Center.