Spina Bifida

Dr. Nabi Darya Vali (AIIMS)MBBS

January 14, 2020

March 06, 2020

Spina Bifida
Spina Bifida

Spina bifida is a type of birth defect or congenital anomaly that occurs when the spine and spinal cord of the foetus do not develop properly. It is a type of neural tube defect (NTD) in which a part of the spine and associated areas form outside the body - this can occur anywhere along the length of the spine. Spina bifida results in damage to the spinal cord and nerves, and it is, therefore, a permanently disabling birth defect.

There are three different types of spina bifida, depending on how the defect takes form: spina bifida occulta, meningocele and myelomeningocele. While the exact cause of spina bifida is not known, doctors have identified a few risk factors that can combine to increase the chances of a baby being born with this congenital defect.

Spina bifida can be diagnosed during prenatal checkups, especially if the mother has a folate deficiency, diabetes, seizure disorders or obesity. An ultrasound during pregnancy, blood test and a test called amniocentesis can usually reveal if your baby is at risk of or has already developed spina bifida.

This birth defect can impair the quality of your child’s life immensely as it is associated with a number of complications like bowel incontinence, urinary incontinence, hydrocephalus (fluid build-up in the brain), mental retardation and paralysis.

Although spina bifida can be treated through surgery, this treatment doesn’t resolve the condition completely. This is the reason why taking preventive measures before and during pregnancy is the best way to reduce the risk of spina bifida.

What is spina bifida?

Spina bifida is a type of neural tube defect that happens in the first few weeks of pregnancy, as the baby’s neural tube develops. The neural tube begins as a hollow structure in the embryo and eventually develops into the brain, spinal cord and the tissues around them. The neural tube is one of the earliest structures to be formed in the embryo. A flat neural sheet rolls up and closes to form the neural tube, usually by the 28th or 32nd day after conception. 

This closure of the neural tube is a delicate and complex process. In babies with spina bifida, this neural tube closure does not happen properly. A portion of the neural tube does not close, which leads to the spinal cord, nerve and tissues to spill out of the body and grow outside it.

Spina bifida types

There are three different types of spina bifida: spina bifida occulta, meningocele and myelomeningocele. The symptoms for each type of spina bifida are different, although they all lead to complications of a similar nature.

Spina bifida occulta

This is the mild form of spina bifida. The spinal cord and tissues stay occulta or hidden inside the baby, but the lower spinal area does not develop properly.

This type of spina bifida might not have a visible mark, or can be located by a birthmark, dimple or hairy patch over the affected area.

Although it is not clearly visible, this type of spina bifida can lead to bowel and urinary disorders, restricted movement below the hips and other complications.

Meningocele

This is the moderate and rarest form of spina bifida. A fluid-filled sac that encloses the spinal cord grows outwards, but this sac does not contain the spinal cord and nerves.

This type of spina bifida can cause movement disorders, bladder issues, hydrocephalus (excess fluid in the brain) and mental retardation.

Myelomeningocele

Also known as open spina bifida, this is a severe type of spina bifida. The outgrowth of the fluid-filled sac in this case also consists of a portion of the spinal cord and nerves.

This sac fully exposes the damaged nerves and tissues, and so a baby with this type of spina bifida will have severe disabilities and be prone to life-threatening infections throughout his or her life.

Causes of spina bifida

While doctors and scientists cannot pinpoint any one reason for spina bifida, they believe that a combination of factors can cause it.

  • Genetics: Although spina bifida is supposed to be genetically passed on by one or both parents, the American Association of Neurological Surgeons opines that 95% of babies with spina bifida are born to parents who have no family history of the condition.
  • Mother's health: Women with certain chronic diseases, including diabetes and seizure issues, are at a greater risk of birthing babies with spina bifida.

Risk factors of spina bifida

Even though doctors do not yet know precisely what causes spina bifida, they have identified certain risk factors that increase the chances of it occurring. Keeping a check on these risk factors can reduce the chances of spina bifida to a large extent.

Some of these risk factors are:

  • Mom-to-be is on anti-seizure medication or has diabetes.
  • Mom-to-be is older than 35 at the time of her first pregnancy.
  • Mom-to-be has a vitamin B deficiency.
  • The parents-to-be already have a child/children with a neural tube defect or Down syndrome.
  • Mom-to-be is obese.
  • Mom-to-be has high body temperature during pregnancy.

Folate deficiency may cause spina bifida

Folate is the natural form of vitamin B9. It’s very important for the healthy development of a baby, and a vitamin B deficiency can cause spina bifida and other neural tube defects.

The synthetic form of folate, called folic acid, is found in nutritional supplements and fortified foods, and pregnant women are compulsorily recommended doses of it to take during the gestation period.

Read more: Vitamins and minerals you need during pregnancy

Family history of spina bifida may increase the risk for future babies

Parents who have had one child with spina bifida are likely to have another baby with the same defect. According to the American Association of Neurological Surgeons, the second baby has a 2-3% increased risk, and the third baby has 10% increased chances of getting spina bifida.

A woman born with a neural tube defect is also likely to give birth to a child with spina bifida. However, the role of family history and genetics in causing spina bifida is not fully understood yet, and babies with no genetic predisposition have also been born with this neural tube defect.

Diabetes may lead to spina bifida

Women who suffer from diabetes, or do not have well-controlled blood sugar levels, are more likely to have a baby with spina bifida.

Anti-seizure medications may cause spina bifida

Some anti-seizure medications can hamper the body’s ability to synthesize folate or folic acid. If the mother is on these medications during pregnancy, then it can increase her likelihood of having a baby with spina bifida.

Obesity may cause spina bifida

If the mother is obese prior to getting pregnant, then it is more likely that she will have a baby with spina bifida.

Obesity is defined as a body-mass index of 30 or above.

Increased body temperature can lead to spina bifida

If the mother has a high body temperature or hyperthermia in the early weeks of pregnancy, due to fever during pregnancy or the use of sauna and hot tubs, then it is slightly more likely that her baby will have spina bifida.

Prevention of spina bifida

The best way to prevent spina bifida is by taking enough folic acid before you get pregnant and for the entirety of the first trimester when you do. Here’s how to go about introducing folic acid into your diet:

  • You should take 400-800 micrograms of folic acid while you’re trying to get pregnant and until the time when you are 12 weeks pregnant. A microgram is one-thousandth of a milligram.
  • If you did not take folic acid before you got pregnant, then you should start immediately and continue until the end of your first trimester.
  • Folic acid tablets are found in most pharmacies and should be taken when recommended by the doctor. All women of childbearing age who are planning to have children should be taking folic acid supplements.
  • Apart from taking synthesized folic acid tablets, you should also eat foods rich in folate or folic acid, like beans, peas, citrus fruits, egg yolks, milk, avocados, broccoli and spinach
  • If you are at a higher risk of getting spina bifida, then your doctor might give you a higher dose of folic acid supplement.

Diagnosis of spina bifida

Spina bifida can be diagnosed during pregnancy or after the baby is born. If the mother receives proper prenatal care, then it’s likely that the risks of spina bifida will be identified during the routine tests and screenings recommended for the mother. The following prenatal tests can diagnose spina bifida and other neural tube defects.

Alpha-fetoprotein (AFP) test

Usually done between the 16th and 18th weeks of pregnancy, the AFP test is a blood test to measure the levels of alpha-fetoprotein produced by the baby.

This type of protein is produced by the baby while in the womb, and amounts of it disperse into the mother’s blood via the placenta.

If the AFP levels are high in the mother, then there is a chance that the baby has a neural tube defect. However, AFP levels can be high for other reasons as well. For example, in the case of twin pregnancy or multiple foetuses.

Amniocentesis

A small sample of the amniotic fluid that surrounds the baby is taken in this test to measure the AFP levels of the baby. If the AFP levels are high, then the baby has a neural tube defect. However, small or closed neural tube defects cannot be determined through this test.

Prenatal ultrasound

Pregnant women are recommended to go for an ultrasound three to five during their pregnancy because this imaging test is a good way to monitor the development of the baby’s organs.

The first ultrasound during pregnancy may be done as early as the 6th week of the pregnancy and the 7th week of pregnancy, to check the baby's heartbeat.

The second ultrasound, done between the 11th week of pregnancy and the 13th week of pregnancy, is called the NT Scan. This ultrasound helps to detect and diagnose neural tube defects, including spina bifida, as well as Down syndromeTurner syndrome and congenital heart disease.

The third ultrasound is done in the fifth month of pregnancy (this is also known as the level 2 ultrasound during pregnancy). The next one is at week 26 and last one, a couple of weeks before delivery. Most women may forgo the fourth ultrasound at week 26, based on the recommendation of their obstetrician/gynaecologist.

If your child is at high risk for an NTD, your doctor may recommend a double marker or triple marker NT scan. NT scan stands for nuchal transparency scan.

Diagnosis after birth

If spina bifida is not diagnosed during pregnancy - which is likely if the mother did not get appropriate prenatal care - then it can be diagnosed through the following after the baby is born:

  • A hairy patch, dimple or birthmark on the back can be a primary indication of spina bifida occulta. Other types of spina bifida are more easily visible because of the outgrown sac that contains spinal fluid, and may also have spinal cord and nerves.
  • The doctor will then recommend an X-ray, MRI scan or CT scan to get a clearer image of the baby’s spine to determine the type and severity of the neural tube defect.

Treatment of spina bifida

While it’s best to completely avoid spina bifida by taking proper prenatal care and enough folic acid while you’re pregnant, in some cases spina bifida becomes unpreventable via these methods. In this case, spina bifida is treated through surgery. It’s important to remember that surgeries do not cure spina bifida, but can stop its progression and reduce complications.

Foetal surgery for spina bifida

This type of surgery is done to correct spina bifida defects while the baby is still in the uterus, and is usually done if the foetus is diagnosed to have the most severe form of the condition, known as myelomeningocele. In this type of surgery, foetal surgeons open the uterus and close the opening in the baby’s back, thereby reducing the progression of spina bifida.

Gynaecologists recommend that foetal surgery should be done only at speciality centres, by surgeons experienced in this type of surgery. This is because having a foetal surgery raises more complications for both mother and baby, and the follow-up care needs to be even more intensive.

Infant surgery for spina bifida

If a baby is born with spina bifida, then infant surgery is done within the first 48 hours. In this case, the surgeons put the spinal nerves back in the baby’s spinal tube and close the muscle and skin. Apart from the neurosurgeon who executes this surgery, a plastic surgeon might need to be on hand if the affected area is too large. The target of this surgery is to repair the exposed part of the spinal cord to minimise future injuries and infections. 

According to the American Association of Neurological Surgeons, 80-90% of children born with spina bifida also suffer from hydrocephalus or the building up of excess cerebrospinal fluid in the brain, which increases the pressure in the brain and can lead to further complications. In this case, a ventricular shunt needs to be placed in the brain. This shunt will reduce the spinal fluid build-up for the rest of the patient’s life, but it needs to be replaced several times during the remaining lifetime.

Follow ups for spina bifida surgery

If a baby goes through surgery - foetal or infant - to treat spina bifida, then regular follow-ups are imperative to reduce deteriorations in the condition for the rest of his or her life. Most deteriorations in spina bifida are now treatable, but follow-ups can help the doctors create a baseline of neurological and muscle function and treat the patients according to their risk factors when needed.

Paraplegic treatment for spina bifida

If the baby is born with myelomeningocele, then the chances are that muscular movements below the location of spina bifida will be restricted or not possible. In this case, the baby will be paraplegic (has no movement below the hips) and will need braces and wheelchairs as he or she grows up depending on the extent of paraplegia.

If the hydrocephalus in these babies is treated and kept under control, they will not have much brain damage and may lead active and productive lives despite paraplegia.



References

  1. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; What is Spina Bifida?
  2. American Association of Neurological Surgeons. [Internet] United States; Spina Bifida
  3. National institute of neurological disorders and stroke [internet]. US Department of Health and Human Services; Spina Bifida Fact Sheet
  4. Stanford Children's Health: Lucile Packard Children's Hospital [Internet], Stanford. USA; Spina Bifida in Children
  5. National Health Service [Internet]. UK; Spina Bifida
  6. Singh, Sangram and Chourishi, Vidya, To study the epidemiology of spina bifida at our centre in India. Cerebrospinal Fluid Res. 2009; 6(Suppl 2): S3. PMCID: PMC2786138
  7. Fletcher, Jack M. and Brei, Timothy J. Introduction: Spina Bifida—A Multidisciplinary Perspective. Dev Disabil Res Rev. 2010; 16(1): 1–5. PMID: 20419765
  8. Copp, Andrew J. Spina Bifida. Nat Rev Dis Primers. 2015; 1: 15007. PMID: 27189655
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