The human nervous system develops from a small, specialized plate of cells (the neural plate) along the back of an embryo. Early in fetal development, the edges of this plate begin to curl up toward each other, creating the neural tube-a narrow sheath that closes to form the brain and spinal cord of the embryo. As development progresses, the top of the tube becomes the brain and the remainder becomes the spinal cord.
This process is usually complete by the 28th day of pregnancy. But if problems occur during this process, the result can be brain disorders called neural tube defects, including spina bifida.
What is spina bifida?
Spina bifida, which literally means “cleft spine,” is characterized by the incomplete development of the brain, spinal cord, and/or meninges (the protective covering around the brain and spinal cord). It is the most common neural tube defect in the United States-affecting 1,500 to 2,000 of the more than 4 million babies born in the country each year. There are an estimated 166,000 individuals with spina bifida living in the United States.
Spina Bifida Occulta (oh-cull-tuh)
In this form, there is an opening in one or more of the bones (vertebrae) that make up the spine. These openings can be seen by X-ray only. The spinal cord, nerves and skin covering are normal. In fact, up to 10% of all Americans may have this most mild form of the spina bifida. In most cases Spina Bifida Occulta causes no problems.
Spina Bifida Aperta (ay-per-tuh)
In these forms, the neural tube does not close, and parts of the bones (vertebrae) that make up the spine are missing. A cyst or lump pokes out from the opening in the spine. There are 2 types of spina bifida aperta:
The cyst is covered with skin and most of the time there is minimal, if any, paralysis. Most children with meningocele grow normally. Your child with meningocele should be checked for fluid on the brain (hydrocephalus) and bowel and bladder problems so they can be treated promptly.
This is the most severe form of neural tube defect. The open defect contains nerve roots of the spinal cord and the cord itself. There may or may not be a cyst that can be seen. Most often there is damage to the nerves, which cannot be reversed. Your child will most likely have some degree of limb paralysis, sensory, bladder and bowel problems. Prompt surgery helps prevent further nerve damage from infection or trauma.
A child with meningomyelocele also often has:
• Fluid on the brain (hydrocephalus). A child may need a tube (shunt) to help the flow of cerebrospinal fluid back into the child’s body. About 90% of children with meningomyelocele have hydrocephalus.
• Some degree of leg paralysis. This varies by child and the level of their defect on the spinal cord.
• Bowel and bladder problems, which can be managed well.
• Compression of the brain at the base of the skull (this is called Chiari II (key-are-ee) Malformation).
• A brain difference and learning disabilities. At least 70% of children with spina bifida have normal intelligence, although most children have learning problems. Some intellectual delays can be more severe.
What causes spina bifida?
The exact cause of spina bifida remains a mystery. No one knows what disrupts complete closure of the neural tube, causing a malformation to develop. Scientists suspect that the cause is multifactoral: genetic, nutritional, and environmental factors play a role.
Research studies indicate that insufficient intake of folic acid-a common B vitamin-in the mother’s diet is a key factor in causing spina bifida and other neural tube defects. Prenatal vitamins that are prescribed for the pregnant mother typically contain folic acid as well as other vitamins.
What are the signs and symptoms of spina bifida?
The symptoms of spina bifida vary from person to person, depending on the type and level of involvement. Closed neural tube defects are often recognized or identified early in life due to an abnormal tuft or clump of hair or a small dimple or birthmark on the skin at the site of the spinal malformation.
Meningocele and myelomeningocele generally involve a fluid-filled sac-visible on the back protruding from the spinal canal in meningocele, the sac may be covered by a thin layer of skin. In most cases of myelomeningocele, there is no layer of skin covering the sac and an area of abnormally developed spinal cord tissue usually is exposed.
What are the complications of spina bifida?
Complications of spina bifida range from minor physical problems to severe physical and mental disabilities. It is important to note, however, that most people with spina bifida have normal intelligence. Children with myelomeningocele and/ or hydrocephalus (excess accumulation of cerebrospinal fluid in and around the the brain) may have learning disabilities, including difficulty paying attention, problems with language and reading comprehension, and trouble learning math.
Spina bifida’s impact is determined by the size and location of the malformation, whether it is covered by skin, and which spinal nerves are involved. All nerves located below the malformation are affected to some degree. Therefore, the higher the malformation occurs on the back, the greater the amount of nerve damage and loss of muscle function and sensation.
Can neural tube defects be prevented?
Studies have found that the B-vitamin, folic acid, may help to prevent spina bifida in some cases. Women who have a family history of these defects and could become pregnant should take a vitamin with 4000 micrograms of folic acid daily. Use this vitamin only if recommend by your healthcare provider. They should also eat foods rich in folic acid such as green vegetables and whole grains. The key is having enough folic acid in the system before and during the early weeks of pregnancy, before the neural structures close.
How is spina bifida detected?
Blood tests of the mother and an ultrasound of the baby in the uterus may find the defect. Most health care providers offer pregnant women a blood test called the maternal serum alpha-fetoprotein (MSAFP) screening test. It is part of the “triple screen” test. When a neural tube defect is diagnosed before birth, health care providers can provide you with information and support. They can plan for the best method of delivery, often by cesarean section, to prevent infection and damage to the affected nerves.
Can the disorder be prevented?
Folic acid, also called folate, is an important vitamin in the development of a healthy fetus. Although taking this vitamin cannot guarantee having a healthy baby, it can help. Studies have shown that by adding folic acid to their diets, women of childbearing age significantly reduce their risk of having a child with a neural tube defect such as spina bifida. Therefore, it is recommended that all women of childbearing age consume 400 micrograms of folic acid daily.
Foods high in folic acid include dark green vegetables, egg yolks, and some fruits. Many foods-such as some breakfast cereals, enriched breads, flours, pastas, rice, and other grain products-are now fortified with folic acid. Most multivitamins contain this recommended dosage of folic acid.
Women who have a child with spina bifida, have spina bifida themselves, or have already had a pregnancy affected by any neural tube defect are at greater risk (anywhere from five to 10 percent of the general population) of having a child with spina bifida or another neural tube defect. These women may benefit from taking a higher daily dose of folic acid before they become pregnant.