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Spina bifidaSpina bifida is a Latinterm which means "split spine" and describes birth defectscaused by an incomplete closure 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 vertebralarches (called clefts). These malformations fall into three categories: spina bifida occulta, spina bifida cystica (myelomeningocele) and meningocele. Spina bifida is a type of neural tube defect. Neural tube defects can usually be detected during pregnancy by AFP screeningor 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, hypertensionand atherosclerosis(coronary artery disease), spina bifida likely results from the interaction of multiple genes and environmental factors. Despite much research on spina bifida we still do not know what causes the majority of human cases. Nevertheless, there is substantial evidence supporting a significant protective effect of folic acid(0.4mgper day) when taken by women early in pregnancy. It is important to note that spina bifida occurs by the 4th 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 0.4mg folic acid) if they are sexually active. Genetic counselingand 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 lumbarand sacralareas. The lumbar nerves control the musclesin the hip, leg, kneeand foot, and help to keep the body erect. The sacral nerves control some of the muscles in the feet, boweland bladderand the ability to have an erection. Some degree of impairment can be expected in these areas.
Types of Spina BifidaSpina Bifida Occulta"Occulta" is the Latin for "hidden." This is a mild form of spina bifida. There is no opening on 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 lesionmay 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, slight ambulatory problems, and slight loss of sensation. 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 surgicallyrepaired shortly after birth. The sac or cyst not only contains tissueand cerebrospinal fluidbut also nervesand part of the spinal cord. The spinal cord is damaged or not properly developed. As a result, there is usually some degree of paralysisand 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 ventriclesof the brain, will also occur. MeningoceleIn this, the least common form, the outer part of some of the vertebrae are split and the meningesare 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. CausesSpina bifida is caused by the failure of the neural tubeto close during embryonicdevelopment. 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. Spina bifida does not follow direct patterns of heredity like muscular dystrophyor 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 of (0.4mg/day) folic acid before and during pregnancy. It is known that women taking certain medication for epilepsyand women with insulin dependant diabetes have a higher chance of having a child with a neural tube defect. It is also more common among those of Gaelicdescent than any other ethnic group. EffectsSpina 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, shuntsurgery to drain fluid from the brain, application of techniques to control bladder and bowel function (such as self-catherizationor diapers), and braces or other equipment to assist in walking. Tethered Cord, 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 MRIswere 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. TreatmentThere 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 in-uterosurgery to correct the spina bifida lesion. In the fourth or fifth month of pregnancy, surgeons have a window of opportunity to perform in-utero surgery by opening the mother's abdomen, and entering the uterusto 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 in-utero surgery will decrease some of the damaging effects of the spina bifida lesion, but it is not a cure. The in-utero surgery is currently undergoing NIHclinical trials and the results of these trials and studies (MOMs study at About.comand Official MOMs Website) will not be completed until 2008. Occurrence ratesIn Canada, spina bifida occurs in about one in every 1000 births. In Western Australia, up until 1996around 2 children in every 1000 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 1000 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 fibrosiscombined. PreventionDoctors and scientistshave found that folic acidcan help to prevent spina bifida. It is recommended that all women of childbearing age and women planning to become pregnant should take at least 0.4 mg/day of folic acid from at least one month before conception, and at least 1 mg/day of folic acid during at least the first three months of pregnancy. Women who have already had a baby with spina bifida or other type of neural tube defect should take extra folic acid: 4 mg/day. 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. PeoplePeople of note born with spina bifida:
External links
es:Espina bífida fr:Spina bifida nl:Spina bifida
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