Spina bifida
From Wikipedia, the free encyclopedia
| ICD-10 | Q05., Q76.0 | |
|---|---|---|
| ICD-9 | 741, 756.17 | |
| OMIM | 182940 | |
| DiseasesDB | 12306 | |
| eMedicine | orthoped/557 | |
| MeSH | C10.500.680.800 | |
Spina bifida (Latin: "split spine") describes birth defects caused by an incomplete closure (an opening) of one or more vertebral arches of the spine, resulting in malformations of the spinal cord. The spinal membranes and spinal cord may protrude through the absence of vertebral arches (called clefts). These malformations fall into three categories: spina bifida occulta, spina bifida cystica (myelomeningocele), and meningocele. Depending on the extent of the types of tissue herniated, these defects can be classified as meningocele, meningoencephalocele, and as meningohydroencephalocoele.
Spina bifida is a type of neural tube defect. Neural tube defects can usually be detected during pregnancy by AFP screening or a detailed fetal ultrasound. Spina bifida may be associated with other malformations as in dysmorphic syndromes, often resulting in spontaneous miscarriage. However, in the majority of cases spina bifida is an isolated malformation. Spina bifida has varying prevalence in different human populations. This and extensive evidence from mouse strains with spina bifida suggests a genetic basis. As with other human diseases such as cancer, hypertension and atherosclerosis (coronary artery disease), spina bifida likely results from the interaction of multiple genes and environmental factors. Despite much research, it is still unknown what causes the majority of cases. Nevertheless, there is substantial evidence supporting a significant protective effect of folic acid (0.4 mg per day) when taken by women early in pregnancy. It is important to note that spina bifida occurs by the fourth week of pregnancy before many women will be aware of a pregnancy, thus it is generally recommended that women of child-bearing age take a folic acid supplement (most multivitamins contain 0.4 mg folic acid) if they are sexually active. Genetic counseling and further genetic testing, such as amniocentesis, may be offered during the pregnancy as some neural tube defects are associated with genetic disorders such as trisomy 18.
The most common locations of the malformations are in the lumbar and sacral areas. The lumbar nerves control the muscles in the hip, leg, knee and foot, and help to keep the body erect. The sacral nerves control some of the muscles in the feet, bowel and bladder and the ability to have an erection. Some degree of impairment can be expected in these areas.
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[edit] Types of spina bifida
[edit] Spina bifida occulta
Occulta is Latin for "hidden." This is the "mildest" form of spina bifida although the degree of disability can vary depending upon the location of the lesion and actually be very severe in some patients.
In occulta there is no opening of the back, but the outer part of some of the vertebrae are not completely closed. The split in the vertebrae is so small that the spinal cord does not protrude. The skin at the site of the lesion may be normal, or it may have some hair growing from it; there may be a dimple in the skin, or a birthmark. People with this form may have incontinence, ambulatory problems, loss of sensation, deformities of the hips, knees or feet and loss of muscle tone. Depending on the location of the lesion, intense pain may occur originating in the lower back, and continuing down the leg to the back of the knee. Other related problems that may occur include a Chiari Malformation most likely type I, scoliosis, and tethered cord. Many people with this form do not even know they have it, or symptoms do not appear until later in life.
[edit] Spina bifida cystica (myelomeningocele)
In this, the most serious form, the meningeal membranes that cover the spinal cord and part of the spinal cord protrude through a cleft, forming a sac or cyst, and are clearly visible. In developed countries, this opening is surgically repaired shortly after birth. Additionally, in the U.S. the National Institute of Child Health and Human Development (NICHD) is currently involved in a fetal intervention study. (MOMS).
The sac or cyst not only contains tissue and cerebrospinal fluid but also nerves and part of the spinal cord. The spinal cord is damaged or not properly developed. As a result, there is usually some degree of paralysis and loss of sensation below the damaged vertebrae. The amount of disability depends very much on where the spina bifida is and the amount of nerve damage involved. Many children and adults with this condition experience problems with bowel and bladder control. In approximately 90% of the people with myelomeningocele, hydrocephalus, extra fluid in the ventricles of the brain, will also occur.
[edit] Meningocele
In this, the least common form, the outer part of some of the vertebrae are split and the meninges are damaged and pushed out through the opening, appearing as a sac or cyst, which contains both the meninges and cerebrospinal fluid. The nerves are not usually badly damaged and are able to function, therefore there is often little disability present. There are usually no negative long-term effects, although problems have been known to arise.
[edit] Causes
Spina bifida is caused by the failure of the neural tube to close during embryonic development. Normally the closure of the neural tube occurs around the thirtieth day after fertilization. However, if something interferes and the tube fails to close properly, a neural tube defect will occur. Neural tube defects include the conditions of anencephaly, encephalocele, and spina bifida.
Spina bifida occurs in the first month of pregnancy, often before the woman knows that she is pregnant, and is associated with ventriculomegaly
Spina bifida does not follow direct patterns of heredity like muscular dystrophy or haemophilia. Studies show that a woman who has had one child with a neural tube defects such as spina bifida, have about a 3% risk to have another child with a neural tube defect. This risk can be reduced to about 1% if the woman takes high doses (4 mg/day) of folic acid before and during pregnancy.
It is known that women taking certain medication for epilepsy, such as valproic acid, which is a known folate antagonist (with folate being known to reduce the incidence of spina bifida) or carbamazepine can increase the chances of having a child with spina bifida. Women with insulin dependent diabetes have a higher chance of having a child with a neural tube defect, as well. It is more common among those of Gaelic descent than any other ethnic group.
[edit] Prevention
There is no single cause of spina bifida nor any known way to prevent it entirely. However the FDA has issued guidelines to help reduce the chances. Doctors and scientists have found that lack of folic acid is a contributing factor of spina bifida. The FDA and UK recommended amount of folic acid for women of childbearing age and women planning to become pregnant is at least 0.4 mg/day of folic acid from at least one month before conception, and continued for the first 12 weeks of pregnancy.[1] Women who have already had a baby with spina bifida or other type of neural tube defect, or are taking anticonvulsant medication should take a higher dose of 4–5 mg/day.[1] As yet it is unknown how or why folic acid helps to prevent spina bifida. Sources of folic acid include: whole grains, fortified breakfast cereals, dried beans, leaf vegetables, fruits.[2]
[edit] Effects
Spina bifida results in varying degrees of paralysis, absence of skin sensation, incontinence, and spine and limb problems depending on the severity and location of the lesion damage on the spine. In very rare cases, cognitive problems also result.
Most babies born with the condition will need surgeries to correct spinal, foot or leg problems, shunt surgery to drain fluid from the brain, application of techniques to control bladder and bowel function (such as self-catherization or diapers), and braces or other equipment to assist in walking.
Tethered Spinal Cord syndrome, with symptoms such as lower body pain, leg weakness, incontinence, scoliosis, numbness, is a common problem associated with spina bifida. Indeed 100% of spina bifida myelomeningocele patients have Tethered Cord, caused by the spinal cord damage when it is repaired by surgery soon after birth, and the resulting natural scar tissue buildup. However many do not show symptoms of Tethered Cord until later in life or never at all. Before MRIs were invented, Tethered Cord could only be detected through symptoms or surgery and therefore those born before the invention of the MRI, and without symptoms, may not know they have it, or even what it is. If, or when, symptoms show up later in life it can often be a difficult process to discover the correct diagnosis, by which time further damage has been done.
According to the Spina Bifida Association of America (SBAA), over 73% of people with spina bifida develop an allergy to latex, ranging from mild to life-threatening. The common use of latex in medical facilities makes this a particularly serious concern.
[edit] Treatment
There is no cure for spina bifida. To prevent further drying and damage of the nervous tissue and to prevent infection, doctors operate as soon as possible to close the opening on the back, but there is no operation that can fix damaged nerves. During the operation, the spinal cord and its nerve roots are put into place and covered with skin.
Doctors are now experimenting with and evaluating the efficacy of fetal surgery to correct the spina bifida lesion in-utero. In the fourth or fifth month of pregnancy, surgeons have a window of opportunity to perform fetal surgery by opening the mother's abdomen, and entering the uterus to operate on the spina bifida lesion found on the fetus. Skin grafts are used to cover the exposed spinal cord and protect the spinal cord from further damage caused by prolonged exposure to amniotic fluid. It is believed that the fetal surgery will decrease some of the damaging effects of the spina bifida lesion, but it is not a cure. The fetal surgery is currently undergoing NIH clinical trials and the results of these trials and studies (MOMs study at About.com and Official MOMs Website) will not be completed until 2008.
Children with severe spina bifida require long-term, intensive therapy that is designed to encourage development and prevent deterioration in physical abilities and kidney function. Surgery may be needed to close the opening in the spinal column and to treat the associated hydrocephalus, bladder and kidney abnormalities and physical deformities.
[edit] Occurrence rates
In Canada, spina bifida occurs in about one in every 1,000 births.
In Western Australia, up until 1996 around 2 children in every 1,000 were born with a neural tube defect. Since 1996, as a result of the folic acid campaign, the figure has dropped to 1.3 children per 1,000 births.
In the United States, spina bifida occurs in about 7 out of 10,000 live births. More children in the U.S. have spina bifida than have muscular dystrophy, multiple sclerosis, and cystic fibrosis combined.
[edit] People
People of note born with spina bifida:
- Jean Driscoll[1], Olympian and eight-time Boston Marathon winner
- Tanni Grey-Thompson, Welsh Paralympian
- Lawrence Gwozdz, U.S. saxophonist
- Blaine Harrison, of the British band Mystery Jets
- John Mellencamp, U.S. rock and roll musician
- Jeffrey Tate, British conductor
- Hank Williams, U.S. country music singer
- Justin Yoder, American soap box racer
- Edward Hancock II, American Writer
[edit] Footnotes
- ^ a b Why do I need folic acid?. NHS Direct (27/04/2006). Retrieved on 2006-08-19.
- ^ Folic Acid Fortification. FDA (February 1996).
[edit] Related Articles
[edit] External links
- Spina Bifida Research Resource A partnership between scientists and families to find the causes of spina bifida
- UCSF Fetal Treatment Center: Myelomeningocele (Spina Bifida)
- Management of Myelomeningocele Study (MOMS) - NICHD study researching fetal treatment of myelomeningocele
- Canadian Health Network - Search Results for spina bifida
- the International Federation for Spina Bifida and Hydrocephalus (IF) - the umbrella organisation for national spina bifida and hydrocephalus organisations
- Fetal Care Center of Cincinnati: Fetal Surgery for Spina Bifida / Myelomeningocele
- Center for Spina Bifida at Gillette Children's Specialty Healthcare
- Association for Spina Bifida and Hydrocephalus
