What Is Spina Bifida?
Spina bifida is a condition resulting from the brain, skull, spinal cord, and spine malformation to varying degrees that occur within the first month after conception (pregnancy). This condition is a form of neural tube defect (NTD). The severity of the condition varies from person to person, where some show very mild symptoms which do not require any treatment. In other cases, where the newborn is affected by severe symptoms like open lesions over the spine, the nerves and the spinal cord may be damaged.
What Are the Different Types of Spina Bifida?
There are three types, these are
Spina bifida occult is a hidden spot in the spine, where the newborn affected by this form does not show any symptoms as it is the mildest and most common form of spina bifida. This form does not require any treatment. In those newborns who are affected by this form, skin covers the deformity in the spinal bone.
This is the most uncommon type, where the membrane covering the spinal cord called the meninges, causes a lump sac in the back. It is quite severe compared to spina bifida occulta, where it is corrected through surgery which may result in mild nerve damage. The infant affected by this form will not have any neurological issues.
Myelomeningocele is the most severe form of all, and the infant affected will have incomplete development of the spinal cord, and the undeveloped parts protrude through the back. These protruding cords are surrounded by a sac that contains cerebrospinal fluid and blood vessels. The skin does not cover these protruded cords and the nerves and tissues are exposed.
What Causes Neural Tube Defects?
The embryonic tissues, which will later specialize to become the central nervous system (brain and spinal cord), the skull, and the spine, start out as a flat plate that rolls into a tube (neural tube). Defects in the neural tube may be due to:
These have been implicated as the cause of disruption of the normal formation process leading to an incomplete neural tube.
What Complications Do Neural Tube Defects Cause?
Defects in the neural tube can cause the brain to form outside the skull.
It may lead to abnormal structure of the brain and skull leading to compression of the lower brain.
It may lead to abnormal structure of the cerebrospinal fluid circulation causing ventricular enlargement.
Defects in the Spine, and Spinal Cord - The defects in the spine and spinal cord can range from an asymptomatic opening in the lower lumbar spine (spina bifida occulta) to more severe forms, including defects in the bone and covering of the nerves or dura (meningocele) or most severe, a defect in the bone, dura, and an incompletely formed spinal cord exposed to the environment (myelomeningocele). The thin layer of tissue present over the spinal cord and cerebrospinal fluid containing space around it in meningocele and myelomeningocele usually ruptures, if left untreated, leading to meningitis (bacterial infection around the central nervous system) which can lead to more severe disability or death. Usually, these defects are in the posterior midline.
Why Is Folic Acid Intake Essential for Women?
Neural tube defects occur between 0.1 to 1 per thousand births in developed countries but are significantly higher in undeveloped countries. The intake of 400 micrograms of folic acid through the daily food intake of women of childbearing age regularly before they become pregnant substantially reduces but does not eliminate the possibility of occurrence.
How Is Spina Bifida Condition Diagnosed During Pregnancy?
Spina bifida can be diagnosed during pregnancy but not always, some tests performed are:
This blood test screens the amount of AFP (alpha-fetoprotein) in the blood, which is performed during the 16th and 18th week of pregnancy. Those women who carry fetuses with spina bifida condition show a raise of AFP about 75 to 80 percent.
An image can be formed where the fetus spine is spotted.
The fluid from the tube is collected for testing the level of protein.
What Treatments Are Available for Neural Tube Defects?
Surgery for meningocele and myelomeningocele closes the potential for exposure of the spinal cord to the environment and usually protects it from further damage. Unfortunately, because the nerves are not well-formed, permanent disability and dysfunction, including loss of bladder, bowel, and sexual function as well as significant weakness or paralysis of at least the lower leg and foot, will still occur in the case of myelomeningocele. Despite this impairment, many children can learn to ambulate with bracing and crutch or cane devices.
The obstruction of cerebrospinal fluid flow (hydrocephalus) leads to increasing pressure on the brain, which lowers the blood supply to the neurons (nerve cells) and directly impairs their development. The process often accelerates after surgery for the myelomeningocele because its escape outside the body, which can lead to infection, is prevented. In the first two years of life, the head may abnormally enlarge (macrocephaly) as the plates that form the skull are not yet fused. Sometimes the hydrocephalus delays its progression until the child is older and skull plates have already closed, leading to the rapid onset of blindness, confusion, coma, and then death.
It is now well known that surgery for hydrocephalus in this situation results in most children functioning within the realm of normal intelligence, while no treatment in the face of progressive hydrocephalus certainly will result in permanent loss of intellectual function, coordination, vision, and even death. The most common treatment for hydrocephalus is the placement of a ventriculoperitoneal shunt (a tube and valve system that controls pressure or flow) which creates a detour of the cerebrospinal fluid from the brain to the peritoneal space (the space between the abdominal organs), where it is absorbed.
Newer alternatives involve placing a surgical telescope in the brain and attempting to open a channel to restore flow which may also include destroying the choroid plexus (tissue that produces the cerebrospinal fluid). The advantage of these newer procedures over traditional shunt surgery is controversial. Those who do undergo this type of procedure may not respond and still require a ventriculoperitoneal shunt. Unfortunately, ventriculoperitoneal shunts may suddenly stop functioning or become infected, needing repeat surgery. For reasons not always clear, a subset of children ends up having multiple operations, especially in the first few years of life.
What Is Tethered Spinal Cord Syndrome?
Occasionally at or near adolescence, a child with a history of myelomeningocele surgery will start to lose what lower extremity function they previously had. It is theorized that tethering of the spinal cord (restriction of the movement of the spinal cord up the spinal canal, which normally occurs with growth) causes mechanical disruption and/or decreased blood supply, leading to further dysfunction.
This can be difficult to assess as MRI (magnetic resonance imaging), which is used to evaluate the spinal cord, most often shows the spinal cord to be below its normal position and be tethered even in those with stable function.
The treatment of tethered cord syndrome for a child with a history of myelomeningocele surgery can be a difficult decision. Often, anxious parents feel the desperation in wanting more function and may give a misleading history of loss of function. Some have advocated this type of surgery as a way to restore control of bladder or bowel function. Still, this loss of function is due to the original incomplete formation of the nerves rather than a later tethering in most cases.
In the past, surgery was often delayed for some time for spina bifida and the associated hydrocephalus with the idea that these children would be sentenced to live poor-quality lives. But this has been proven wrong. Today, most experts advocate surgery as early as possible to reduce the risk of infection and further injury. While the child is in the mother’s womb, attempts at the surgery are made in a few centers, but the benefit of this procedure which puts both mother and child at risk over early intervention after birth is not yet clear.
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