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Spina Bifida


Spina bifida is one of the most common congenital defects, occuring within the first 25 days of pregnancy. This deformity is known as a neural tube defect. In addition to an obvious gap in the skin covering the spine, the vertebrae and the nervous system is damaged. As a result of these defects the child will have some degree of paralysis. Most children and adults will have problems with bowel and bladder control. Spina bifida is a result of lack of absorption of folic acid . The quality of food can have an influence on this, though other preventive measures may also be necessary. More than 85 % of children with spina bifida also have hydrocephalus or develop this at a later stage. Spina bifida is a condition that cannot be cured. In most cases several surgical interventions are needed, such as the closure of the back after birth. Good medical care and intensive training can prevent many complications and improve the quality of life. The three most common types of spina bifida are: spina bifida occulta, meningocele and myelomeningocele.

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Spina Bifida

Spina Bifida is a fault in the spinal column in which one or more vertebrae (the bones which form the backbone) fail to form properly, leaving a gap or split, causing damage to the central nervous system. To help understand what it is, let us explain about the composition of the nervous system.

The Central Nervous System
The central nervous system consists of the brain and the spinal cord. All activities are controlled by the brain which receives information from touching, seeing, feeling, tasting and hearing - responding to this information by initiating the appropriate movements of different parts of the body. Messages from the brain are carried to different parts of the body by the spinal cord which runs down the centre of the spinal column. This communication system for the body is very important and needs protection

The Spine
The spine is made up of 33 bones or vertebrae. The vertebrae have two main functions. One is to provide anchorage for muscles so that we can move as we dictate to those muscles. The other is to provide protection to the spinal cord.

The Neural Tube
The central nervous system and spine develop between the 14th and 28th day after conception. Spina bifida occurs when there is a failure of development of the boney canal which surrounds the brain and spinal cord. In the spine, the affected vertabrae have a defect posteriorly (at the back) so that a boney ring does not completely surround the spinal cord. This leaves a gap so that, instead of the posterior arm being whole it is divided - that is bifid. The fault may occur in one or more of the vertabrae but it is most common around waist-level.

Types of Spina Bifida
There are three main types of spina bifida : Spina Bifida Occulta, Spina Bifida Cystica Meningocele and Spina Bifida Cystica  Myelomeningocele (meningomyelocele)

· Spina Bifida Occulta (hidden)
This is a very mild and common form and very rarely causes disability. There is a slight deficiency in the formation of (usually) one of the vertebrae. It may have visible signs of a dimple or small hair growth on the back. However, many people are unaware that they have spina bifida occulta as they have no symptoms or signs.

How many people are affected?
Many people have this condition. One survey suggested the proportion could be one in 10 of the population. The vast majority of these will have no symptoms or problems. Spina bifida occulta may be detected by X-ray when, for example, investigations of back injury are being made. In such cases, it can be extremely frightening to be labelled as having spina bifida but it must be emphasised that, for the vast majority, it is of no consequence whatsoever. Women with spina bifida occulta should ask their doctor to prescribe the higher dosage of folic acid when they plan to become pregnant - to help reduce the risk of their baby being affected by spina bifida.

Are there any complications ?
Unfortunately, in some cases the cleft in the spine may cause problems. Sometimes the spinal cord may become tethered - that is, caught against the vertebrae. With growth, tension can cause inefficient functioning, affecting bladder control and mobility. If these symptoms are observed, it is important to consult a GP who, if appropriate, can refer to a neurosurgeon.

· Spina Bifida Cystica (cyst-like)
The visible signs are a sac or cyst, rather like a large blister on the back, covered by a thin layer of skin. There are two forms:

  1. Meningocele
    In this form, the sac contains tissues which cover the spinal cord (meninges) and cerebro-spinal fluid. This fluid bathes and protects the brain and spinal cord. The nerves are not usually badly damaged and are able to function, therefore there is often little disability present. This is the least common form.
  2. Myelomeningocele (meningomyelocele)
    Myelomeningocele is the most serious and more common of the two forms of cystic spina bifida. Here the cyst not only contains tissue and cerebro-spinal fluid but also nerves and part of the spinal cord. The spinal cord is damaged or not properly developed. As a result, there is always some paralysis and loss of sensation below the damaged region. The amount of disability depends very much on where the spina bifida is and the amount of nerve damage involved. Many people with this condition have bowel and bladder problems because of damage to the nerves going to the bowel or bladder from the bottom end of the spinal cord.

This is a sac which is formed when the bones of the skull fail to develop. It may contain cerebrospinal fluid only, however, part of the brain may also be present in the sac, resulting in brain damage.

This is where the brain does not develop properly or is absent, and the baby is either still born or dies shortly after birth.

Most babies born with spina bifida also have hydrocephalus (from the Greek hydro = water, cephale = head). This is an accumulation of cerebrospinal fluid which arises from an imbalance in the production and drainage of that fluid.

How and Why Does Spina Bifida Happen?
At present, the cause is unknown, although research continues. Our page on folic acid outlines the research results which led to the Department of Health issuing guidelines about the role that folic acid supplements play in reducing the risk of spina bifida in pregnancy, provided they are taken daily from at least one month before conception and then through to the end of the 12th week of pregnancy. The exact reasons why the tube develops incorrectly are not yet known, but it is probably connected with both genetic and environmental factors. Spina bifida is a defect which is present at birth. In Britain, incidence varies from one area to another. Spina bifida is only partially hereditary. However once there has been an affected pregnancy, there is an increased risk of further spina bifida pregnancies. The risk of an adult with spina bifida having a child with a similar condition is approximately 3% or 1 in 35.

Spina Bifida Occulta

This is a mild form of spina bifida which is very common. Estimates vary but between 5% and 10% of people may have spina bifida occulta. It must be emphasised that, for the vast majority of those affected, having spina bifida occulta is of no consequence whatsoever. Often people only become aware that they have spina bifida occulta after having a back x-ray for an unrelated problem. However, for a few (about 1 in 1,000) there can be associated problems.

Why do some people have complications?
The term 'spina bifida occulta' is, in fact, not one but two separate conditions which have completely different consequences. This leads to confusion when such a diagnosis is used without qualification. For the majority of people with spina bifida occulta, it is a minor fault involving one vertebra in the lower back. The unfortunate use of this term for such a minor fault can lead to distress for the person concerned. However, it should be considered as insignificant, both for that person and his or her children.
For a small number of people with spina bifida occulta the fault is more extensive. Either the split in the spine is bigger, or may involve two or more vertebrae. There may be visible signs on the skin such as a mole or naevus (birthmark), a dimple or sinus (hole), or a patch of hair. If these are positioned above the level of the buttocks and in the midline (centrally) there may well be a significant underlying spina bifida occulta. A dimple or sinus that is below the level of the buttocks is usually innocent and does not usually indicate an underlying spina bifida occulta.

For people with spina bifida occulta, there may be associated difficulties which may include: foot deformity, weakness and reduced sensation of the legs, change in hand function, bladder infections and incontinence and bowel problems. These problems arise because the spinal cord becomes tethered to the backbone. Often a child who is previously symptomless may experience difficulties during the rapid growth of adolescence. This is because the nerves of the spinal cord are stretched and the symptoms may become progressively worse. It is important to consult a GP, who, if appropriate, can refer to a neurosurgeon. Specialist scanning procedures such as MRI (magnetic resonance imaging) give a clear picture of the nerves and spinal column and the neurologist will be able to advise on the most appropriate treatment. People with spina bifida occulta and progressive (worsening) symptoms of a stretched or tethered spinal cord need to have an operation on their lower spine to release the tension in the spinal cord. This is often a fairly simple and effective procedure, but occasionally the operation is very complicated and involves a (2% - 5%) risk of failure. It is often possible to improve symptoms in the legs with this operation, but it is rare for bladder function to return to normal. The main purpose of a "detethering operation" is to stop any further deterioration in leg or bladder function and it is important that a neurosurgical assessment is made as early as possible after the onset of symptoms. The operation is probably best done by those neurosurgeons who have a special interest in the condition.

What are the implications?
For the vast majority of people with the non-significant form of spina bifida occulta, there are no known complications and there is no higher risk of having children with spina bifida than there is in the general population.
For those with the more complicated spina bifida occulta, there may be neurological problems which may or may not be present at birth and may be progressive. Those with significant spina bifida occulta have a risk, higher than in the general population, of having children with spina bifida which could be cystica or occulta. This risk is between 2% and 4% and is the same risk that those with spina bifida cystica have of passing on the disability. However, the risk of having a baby with spina bifida can be dramatically reduced by taking folic acid (a B-group vitamin).

Reduce the risk of having a baby with spina bifida
The non-significant form of spina bifida occulta carries no more risk of having children with spina bifida than that for the general population. However, the Government recommends that all women of childbearing age take a daily supplement of 0.4mg of folic acid beginning one month before conception and for the first three months of pregnancy as well as eating a diet rich in folic acid. This is because in the majority of cases, where a baby is born with spina bifida, there is no family history of the disability. For those with the more complicated spina bifida occulta, and therefore an increased risk of having children with spina bifida, it is necessary to take a higher daily dose of folic acid during the same period. This 5mg tablet is only available on prescription.

More information and advice
If you suspect to have spina bifida occulta and are experiencing any of the problems described above, you should ask your GP for referral to a neurologist who can investigate and advise about treatment. Women who have spina bifida occulta and who are planning to have a baby can ask for a referral to a geneticist. He will consider both the family history and individual medical circumstances and will advise on the risk of having a baby with spina bifida.

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