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Spina bifida is a type malformation that occurs during early fetal development. It's known as a type of neural tube defect (NTD), in which either the brain and spine or only the spine fails to develop properly in the womb. There are three types of spina bifida, which vary according to the severity of the malformation:

• myelomeningocele: the most severe form; both the spinal cord and its lining (the meninges) protrude from an opening in the spine
• meningocele: only the lining protrudes
• spina bifida occulta: the mildest form, there is a breach in the spinal vertebrae but it's covered by skin

These malformations are usually in the lower back or at the level of the hips.

The frequency of spina bifida in Canada has been declining gradually. In 1989, the rate was 1.1 per 1,000 total births; in 1996, it was 0.77 per 1,000 total births. This is mainly due to improved diet among Canadian mothers and supplementation with folic acid. There are about 200 spina bifida births each year in Canada.

The exact cause of spina bifida is still unknown. Something goes wrong in the first two months after conception but experts don't really know why. It's been shown again and again that women who have low levels of folic acid (a B vitamin) are more likely to give birth to children with neural tube defects. The assumption is that when the fetus's genes give the order to construct the spine, the necessary chemical building blocks are missing.

There's almost certainly no single spina bifida gene, and it can occur in any pregnancy, yet some people are predisposed to it. Women with a family history of neural tube defects are at increased risk of giving birth to a baby with such a defect. Women who have already had one pregnancy that resulted in spina bifida, whether or not they carried it to term, run about a 2% risk of neural tube defects in each subsequent pregnancy. This is more than ten times the average risk. Still, more than 90% of cases of spina bifida occur in families with no history of the condition.

Most people with spina bifida have some degree of paralysis, usually in the lower body, and need wheelchairs or other aids to get around. The nature of the paralysis depends on the location and severity of the lesion in the spine. In a few cases, mild spina bifida occulta can cause no physical problems at all. There may well be people with this condition who have never been diagnosed and will never suffer any ill effects.

Unfortunately, paralysis is common and often begins in the womb. This means that babies may already have suffered complications of long-term paralysis at the time of birth. This includes having a spine that's too curved at the base, which prevents an infant from lying normally on his or her back. Sometimes the bones of the spine (vertebrae) or other joints may become locked in position, typically in a bent position. Clubfoot and dislocated hips are other common malformations seen at birth.

The nerves that control the bowel and bladder are often damaged in spina bifida, leading to various problems such as severe constipation or incontinence and frequent infections. Over the years, this can put a massive strain on the kidneys, and kidney failure is a leading cause of death in adults with this disease.

Most people with spina bifida also have malformations high in the spinal cord or brain that lead to a dangerous build-up of cerebrospinal fluid (CSF) in the ventricles inside the brain. This is called hydrocephalus. About 75% of people with spina bifida develop this condition at some point. In an infant, it can cause the skull to grow out of proportion to the body. This condition can be treated.

People with spina bifida are of normal intelligence, but for unknown reasons they are more likely than the general population to have learning disabilities such as dyslexia.

The greatest risk of complications in people with spina bifida occurs during the first day of life. Their central nervous system isn't isolated from the rest of the body, so they're at very high risk of developing meningitis, an infection of the lining of the brain and spinal cord. For this reason, newborns with spina bifida undergo surgery to close their spinal lesion in the first few days after birth. Unfortunately, there's no way to repair the damaged nerve tissue, and attempts to intervene and prevent damage before birth have not been successful.

Spina bifida can be easily diagnosed at birth. Myelomeningocele and meningocele are clearly visible, and spina bifida occulta is often suggested by a tuft of hair or skin dimple over the low end of the spine. This can be confirmed with an ultrasound or a magnetic resonance imaging (MRI) scan, which will reveal the size and location of any spinal lesions.

It's also possible to detect it before birth. This can be done with ultrasound, but for screening large numbers of low-risk pregnant women, a blood test that measures levels of maternal serum alpha-fetoprotein (MSAFP) is generally considered reliable. If the test result is positive further tests are performed.

Right now in Canada, women at high-risk (i.e., those with family or personal pregnancy history of spina bifida) are likely to receive both ultrasound and MSAFP screening, while women at low-risk are not screened at all.

There's no cure for spina bifida and nothing can be done to repair the damaged nerves or reconstruct the central nervous system. Although spina bifida is not a progressive condition, some of its complications, such as hydrocephalusmay get steadily worse. For most people, the lesion is closed shortly after they're born, and there is no further treatment of the condition itself.

Progressive hydrocephalus can be treated with the surgical procedure known as a shunt. A pathway is created that leads from the inside of the skull to some other part of the body (usually the abdomen) where the cerebrospinal fluid can be safely drained and reabsorbed. This procedure is often life-saving for a child. As they get older, some children with spina bifida may no longer need their shunt, but it's impossible to tell which children, so shunts are usually left in place indefinitely. Shunts carry a risk of serious infection or blockage, however, and for adults with spina bifida, shunt complications are among the leading causes of death, along with kidney failure.

Most people with spina bifida make it to adulthood, but few live to a ripe old age. Things have improved dramatically over the past twenty or thirty years, when spina bifida was usually fatal in childhood. Although the quality of life for people with spina bifida is better now, a real cure for this disease still seems a very long way off. Prevention remains the key.

Women can reduce their chances of a spina bifida pregnancy by about half by taking an adequate dietary supply (0.4 mg a day) of folic acid. It's useless for women to wait until they're pregnant and then start on folic acid, because spina bifida occurs so early in pregnancy that it's already happened by the time a home pregnancy test reads positive. Folic acid needs to be in a woman's system at the time of conception. Therefore, women who want to become pregnant should be taking 0.4 mg per day all the time.

Since 1998, certain foods in Canada have been fortified with folic acid. This fortification of commercial food provides about 0.1 mg a day in the average diet, enough to reduce neural tube defects by about 20%, but not enough to provide the maximum protection possible. If a woman is thinking of getting pregnant, she should immediately start taking 0.4 mg daily. Folic acid is the most important of all vitamins for a healthy pregnancy.