Neural Tube Defects (NTDs) at a Glance
- NTDs are serious birth defects of the brain and spine that occur during the first month after conception
- 1 in 1,365 babies in Utah has an NTD.
- NTDs affect 3,000 pregnancies in the United States each year.
- Spina bifida, an NTD, is the most common permanently disabling birth defect.
- 70,000 individuals in the United States have spina bifida.
- More children are affected by spina bifida than muscular dystrophy and cystic fibrosis combined.
- More than half of NTDs are preventable.
- All women of child-bearing age should take (at least) 400 mcg of folic acid every day to reduce the risk of NTDs.
- The average lifetime cost for medical treatment, educational services and lost productivity for one individual with spina bifida is $635,763.
Why Is This Important?
The neural tube is an early embryonic structure which forms 18 to 30 days after conceptions. Beginning as a flat plate of tissue, the neural tube then forms two ridges of tissue which fold up and fuse, forming cylinder or tube. This neural tube forms the brain and spinal cord. Neural tube defects occur when the tube fails to close completely, usually before most women even know they are pregnant.
What are the major types of NTDs?
In spina bifida, the most common NTD, the spine fails to properly close. As a result, the bony spine is open and the spinal cord is malformed and exposed. Often a sac is associated with the defect. Myelomengocele and meningocele are types of spina bifida.
A myelomeningocele occurs when the meninges (protective covering of the spinal cord) and spinal nerves protrude through the open part of the spine, often into a sac. This is the most serious type of spina bifida, which causes nerve damage and more severe disabilities.
A meningocele is usually less severe because no nerves extend out through the open part of the spine. Instead, t he protective coatings called the meninges and cerebrospinal fluid are in the sac. Usually there is not nerve damage, although some medical issues may develop.
Anencephaly is a severe NTD where the brain and skull fail to form. Babies with anencephaly do not survive.
An encephalocele is a birth defect in which a sac extends from an opening in the skull. The sac may contain the membranes normally covering the brain (the meninges) and often some brain tissue. The severity is variable.
What is the impact of NTDs?
Neural tubes defects result in significant disabilities and have a significant economic impact.
The most common NTD, spina bifida, has serious, lifelong medical implications. Surgery is needed in the newborn period to close the back. Most individuals with spina bifida will have some degree of weakness and paralysis of the legs and difficulty with bowel and bladder control. There is often an increased risk of urinary tract infections.
About 90% of individuals with spina bifida also have hydrocephalus, extra cerebrospinal fluid accumulation in the interconnecting chambers (ventricles) of the brain, due to a related malformation of the brain called an Arnold-Chiari, type II malformation. The lower part of the brain known as the brain stem abnormally presses down on the spinal canal, causing a blockage. A shunt is surgically placed to redirect the extra fluid and maintain normal fluid pressure in the brain. Individuals with a shunt are at risk for malfunction and infections of the shunt.
Clubfeet and other orthopedic issues also occur. Surgery for a tethered cord is sometimes needed.
Most individuals with spina bifida have normal intelligence, but may have learning disabilities and a slightly lower IQ compared to siblings. Seizures sometimes occur.
The average lifetime cost for medical treatment, educational services and lost productivity for one individual with spina bifida is $635,763 (2002 estimate).
Can NTDs be prevented?
Yes, many NTDs can be prevented by taking a multivitamin containing at least 400 mcg of folic acid at least one month prior to conception.
Folic acid is a B vitamin found in green leafy vegetables, dried beans and fortified foods such as pasta, bread and cereal. Folic acid helps build healthy cells and is important in early fetal development.
Research has shown that folic acid lowers the risk of having a child with a neural tube defect. If all women of childbearing age were to take a multivitamin with folic acid, the occurrence of NTDs could be reduced by 50 to 70%. Since NTDs occur early in pregnancy, often before a woman knows she is pregnant, it is important to take at least 400 mcg of folic acid every day.
Although folic acid use is higher among women in Utah compared to other parts of the US, as of 2003, over half of Utah women of childbearing age do not take folic acid daily. That means more than 25,000 babies each year do not have the benefit of folic acid supplementation in early development.
Who is at risk?
All pregnancies are at risk to have some type of birth defect including a NTD. 3% of all babies born have a recognizable birth defect. 90% of babies with NTDs are born to families with no family history of NTDs. Some women are at an increased risk of having an NTD. Maternal diabetes requiring insulin, the use of certain medications (valproate, depakote tegretol, carbazamine) and having a family history of NTDs increase the risk of having a child with NTD. These women who are at increased risk will benefit from higher amounts of folic acid (usually a daily dose of 4 mg of folic acid) and good medical care for their medical condition.
Genetic, environmental and unknown factors are thought to contribute to the occurrence of NTDs, but more research is needed to understand the cause of NTDs.
How are NTDs detected?
In pregnancy, alpha-fetoprotein (AFP) screening of the mother's blood can identify 80% of pregnancies affected by spina bifida and nearly all with anencephaly. Ultrasound and amniocentesis are also useful for detecting NTDs. Most NTDs are evident at birth by physical exam or imaging studies.
How common are NTDs in Utah?
The Utah Birth Defects Network has tracked cases of neural tube defects in Utah since 1994. 330 cases of NTDs were identified from 1994 to 2003. About one in 1,365 births had a neural tube defect during this time period. This represents about half of the number of cases per year prior to 1992. Since 1994, there is some variability in occurrence rates as shown in the first graph at the top of the right-hand column.
Variation by race and ethnicity is difficult to assess in Utah because of the relatively few births among some groups. Preliminary data suggests a slightly higher rate of neural tube defects in Hispanics, an intermediate rate in whites and a slightly lower rate in Asians. The Utah Birth Defects Network also tracked time trends by race and ethnicity (see the other graphs in the right-hand column). 79% of affected cases were white and 16% were Hispanic.
What is the role of the UBDN in preventing NTDs?
Activities of the UBDN currently include:
1) tracking neural tube defects rates across the state and in different population groups;
2) promoting and evaluating folic acid education among women and health care providers to increase the daily use of folic acid supplements among Utah women; and
3) searching for further clues of causes of NTDs.
What services are available for families who have a child with a NTD?
The Spina Bifida Association of America recognizes these clinics as providers for multidisciplinary medical care for spina bifida in Utah:
Primary Children's Medical Center
Spina Bifida Clinic
100 N. Medical Drive
Salt Lake City, UT 84113
Phone: (801) 588-3382
Shriner's Hospital for Children
Fairfax Ave. at Virginia St.
Salt Lake City, UT 84103
Phone: (801) 536-3621
Developmental services for children with spina bifida from birth to three years of age are provided by the Utah Early Intervention Program, located within the Bureau of Children with Special Health Care Needs, Utah Department of Health. Services include child health assessment, service coordination, occupational and physical therapy, and speech and language therapy. Information on these services is available at: http://www.utahbabywatch.org
Developmental and educational services for children ages three and older are provided by local school districts for children who qualify.
A further resource is the Utah Collaborative Medical Home, which is a project designed to provide information, tools, and resources for Primary Care Physicians to enhance their ability to care for children with special health care needs. Information on the Utah Collaborative Medical Home is available at their web site: http://www.medhomeportal.org
NTD Support Groups and Information Sources
Spina Bifida Association of America (SBAA)
4590 MacArthur Blvd, NW Suite 250
Washington, DC 20007-4226
Fax: (202) 944-3295
Spina Bifida and Hydrocephalus Association of Canada (SBHAC)
220-388 Donald Street
Winnipeg, Manitoba R3B 2J4
Fax: (204) 925-3654
Hydrocephalus Support Group, Inc. (HSG, Inc.)
PO Box 4236
Chesterfield, MO 63006-4236
Phone: (314) 532-8228
Centers for Disease Control National Center on Birth Defects and Developmental Disabilities
1600 Clifton Road
Atlanta, GA 30333
Phone: (800) 311-3435
Phone: (404) 639-3534