Written by Ananya Ganesh
Edited by Anirudh Koneru
Published on 10/31/2020
October is spina bifida awareness month!
Spina bifida is also known as "split spine": spina means "spine" and bifida means "split".
This week's rare disease highlight is on spina bifida, a rare birth defect in which the spinal cord of a baby develops improperly and the spine does not close in the womb.
Description
Spina bifida is a congenital defect (present from birth) that occurs when the brain and spinal cord are not properly formed within the womb. It is a type of neural tube defect (NTD), meaning that the neural tube, which is the component in a growing embryo that goes on to form the brain, spinal cord, and surrounding tissues, is deformed.
Normally, the neural tube is formed at an early stage in the pregnancy, and closes within four weeks of conception. In fetuses and newborns diagnosed with spina bifida, a segment of the neural tube does not close or develop as it should, causing abnormalities in the spinal cord and vertebrae.
Spina bifida may ultimately lead to difficulties with walking and further orthopedic issues, bladder control and urinary incontinence, and accumulation of fluid in the brain (hydrocephalus). Myelomeningocele, a more severe form of spina bifida, may lead to meningitis, or an inflammation in the meninges, the tissues surrounding the brain. This may lead to brain injury.
Signs and Symptoms
Spina bifida has various signs and symptoms, differing according to type and severity. Listed below are some signs and symptoms by the three main types of spina bifida:
Spina bifida occulta:
With this form of spina bifida, there aren’t typically any obvious signs and symptoms, because the spinal nerves are not involved. However, signs can sometimes be seen on the skin of the newborn above the defect, including (but not limited to) an abnormal tuft of hair, or a small dimple/birthmark. These marks on the skin can occasionally be signs of a spinal cord issue, which can be discovered and confirmed with MRI or ultrasound scans in a newborn.
Myelomeningocele:
The spinal canal generally remains open along multiple vertebrae in the lower or middle part of the back. Membranes surrounding the spinal cord and the spinal cord obtrude at birth, forming a visible sac, or protrusion on the back. Tissues and nerves are usually exposed, and in most cases of myelomeningocele, skin does not cover the sac
Meningocele:
Meningocele typically has similar, although less severe, symptoms to myelomeningocele. Meningocele is generally characterized by a fluid-filled sac, visibly protruding from the back, whereas in myelomeningocele, the sac contains part of the spinal cord and its enclosing tissues. In most cases of meningocele, however, the protrusion is covered by a layer of skin.
Etiology
Modern medicine has still been unable to find the cause of spina bifida. It is generally theorized to be a result of a variety of genetic, nutritional, and environmental factors, such as a genetic history of neural tube defects, or a folate (Vitamin B9) deficiency.
Folate (folic acid) deficiency is an important factor that has been connected to neural tube defects in newborns. It is approximated that taking folic acid supplements before conception and during pregnancy may prevent up to 70% of neural tube defects, of which spina bifida is only one.
The consumption of certain medications during pregnancy has also been linked to spina bifida in newborns. Valproate and carbamazepine are used to treat epilepsy and some mental health disorders (like bipolar disorder), and have been linked to spina bifida.
Other factors which may affect likelihood of contracting spina bifida include obesity and diabetes in the mother.
Diagnosis
Modern medicine has still been unable to find a test for spina bifida with 100% accuracy. However, pregnant mothers are typically offered blood screening checks at some point during the pregnancy (generally within the first two trimesters), to test for spina bifida and other neural tube defects.
Spina bifida is primarily screened with maternal blood tests, but the final diagnosis is usually made using ultrasound technology. Given below are a few of the tests that are conducted during the screening:
Maternal serum alpha-fetoprotein (MSAFP) test
A specimen of the mother’s blood is extracted and screened for alpha-fetoprotein, a protein synthesized by the fetus. It is considered normal for small amounts of AFP to have crossed the placenta and entered the mother’s bloodstream, but an abnormally high amount typically points to a neural tube defect, like spina bifida. This is not always accurate, and high amounts of AFP do not always occur in spina bifida.
Additional tests to confirm high AFP quantities
Varying levels of AFP can be due to multiple factors which are not related to neural tube disorders, including fetal age and multiple babies. Doctors generally order a follow-up test for confirmation, and if AFP levels are still high, recommend an ultrasound and further examination.
After the screening, a fetal ultrasound is the most accurate and generally accepted way to diagnose spina bifida. It can be performed in the first and second trimesters, and spina bifida is accurately diagnosed in the second trimester. In a regular pregnancy, this test is crucial to rule out congenital abnormalities.
An advanced ultrasound can also detect specific signs of spina bifida, such as an unenclosed spine, or specific features in the brain and surrounding tissues, that signify spina bifida. In experienced hands, an ultrasound can also identify the type and severity of spina bifida.
If diagnosis of spina bifida is confirmed in the ultrasound, the doctor may prescribe amniocentesis. During this procedure, the doctor uses a needle to remove a sample of fluid from the amniotic sac that surrounds the baby. This examination is important to rule out genetic diseases, even though spina bifida is rarely associated with these.
Mild cases of spina bifida occulta may be diagnosed after birth by plain film X-ray examination. Babies with more severe forms of spina bifida often feel muscle weakness in their feet, hips, and legs that cause deformities that may be present at birth. Doctors may also use MRI or CT scans to get a clear view of the spinal cord or vertebrae. If hydrocephalus (buildup of fluids within the brain) is suspected, they may recommend a CT scan or an X-ray to look for extra fluid inside the brain.
Treatment
There is no empirical cure for spina bifida. However, spina bifida treatment typically depends on the type of spina bifida and the severity. Spina bifida occulta requires treatment only in exceptional cases, but for all the other types, treatment is essential for the child to live normally.
Nerve function in babies with spina bifida can deteriorate after birth if spina bifida isn’t treated. Prenatal surgery for spina bifida is normally conducted before the 26th week of pregnancy. In the process, surgeons expose the mother’s uterus surgically, open the uterus, and repair the spinal cord. In some patients, this procedure can be performed less invasively with a fetoscope through ports in the uterus.
Myelomeningocele requires surgery, and performing it early can help minimize the risk of infection associated with the exposed nerves. Performing surgery early may also contribute towards protecting the spinal cord from additional harm. This procedure involves the placement of the spinal cord and exposed tissue (by the neurosurgeon) inside the body of the baby, and then the enclosure of the tissues inside muscle and skin. Simultaneously, the neurosurgeon might place a shunt inside the brain to prevent hydrocephalus. Surgery may also be conducted soon after birth to close the opening in the spine and treat hydrocephalus.
Recent research has found a correlation between fetal surgery and disability in the child as he/she grows, suggesting that children who had fetal surgery may have reduced disability, and be less likely to require walking aids like crutches. Fetal surgery has increasingly been found to also reduce the risk of hydrocephalus in newborns.
Rarity
Spina bifida is one of the most common permanently-disabling birth defects but it is still counted as a rare disease. It is one of the most common neural tube defects in the United States, even as it only affects about 1,500 to 2,500 of the more than 4 million babies born each year (NIH, 2020). An estimated 166,000 individuals with spina bifida live in the United States today.
In the USA, Hispanic women have the highest chance of having a child affected by spina bifida, when compared to non-Hispanic white, and non-Hispanic black women, with 3.80 children per 10,000 live births being affected. White women are second in terms of risk.
However, prevalence of spina bifida seems to have decreased in recent years, due partly to the efforts of pregnant mothers to follow preventative measures before and during their pregnancies, as well as prenatal testing. Since folic acid fortification began in 1992, there are estimated to have been around 1,300 babies born in the USA every year without a neural tube defect, who would probably have had one, if it were not for fortification.
Resources
Shine (Spina bifida • Hydrocephalus • Information • Networking • Equality)
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Citations
Spina bifida - Symptoms and causes. (2019). Mayo Clinic; https://www.mayoclinic.org/diseases-conditions/spina-bifida/symptoms-causes/syc-20377860#:~:text=Spina%20bifida%20is%20a%20birth,the%20tissues%20that%20enclose%20them.
Spina bifida - Diagnosis and treatment - Mayo Clinic. (2019). Mayoclinic.Org; https://www.mayoclinic.org/diseases-conditions/spina-bifida/diagnosis-treatment/drc-20377865
CDC. (2020, September 1). What is Spina Bifida? Centers for Disease Control and Prevention. https://www.cdc.gov/ncbddd/spinabifida/facts.html
Spina Bifida – Types and Treatment Options. (2020). Aans.Org. https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Spina-Bifida
Spina Bifida Fact Sheet | National Institute of Neurological Disorders and Stroke. (2020). NIH.Gov. https://www.ninds.nih.gov/disorders/patient-caregiver-education/fact-sheets/spina-bifida-fact-sheet
NHS Choices. (2020). Overview - Spina bifida. https://www.nhs.uk/conditions/spina-bifida/
Spina Bifida - NORD (National Organization for Rare Disorders). (2019). NORD (National Organization for Rare Disorders); NORD. https://rarediseases.org/rare-diseases/spina-bifida/
CDC. (2020, August 31). Data and Statistics on Spina Bifida. Centers for Disease Control and Prevention. https://www.cdc.gov/ncbddd/spinabifida/data.html
What is spina bifida? (2018). Shinecharity.Org.Uk. https://www.shinecharity.org.uk/spina-bifida/what-is-spina-bifida
Related Conditions. (2018). Shinecharity.Org.Uk. https://www.shinecharity.org.uk/related-conditons/related-conditions
Spina bifida | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program. (2017). Nih.Gov. https://rarediseases.info.nih.gov/diseases/7673/spina-bifida
NHS Choices. (2020). Causes - Spina bifida. https://www.nhs.uk/conditions/spina-bifida/causes/
NHS Choices. (2020). Treatment - Spina bifida. https://www.nhs.uk/conditions/spina-bifida/treatment/
NHS Choices. (2020). Symptoms - Spina bifida. https://www.nhs.uk/conditions/spina-bifida/symptoms/
Photos:
Desai, R., Marshall, T., & Miller, B. (n.d.). Spina Bifida. Retrieved October 31, 2020, from https://www.osmosis.org/learn/Spina_bifida
Mayo Clinic Staff. (2019, December 17). Spina Bifida. Retrieved October 31, 2020, from https://www.mayoclinic.org/diseases-conditions/spina-bifida/symptoms-causes/syc-20377860
SickKids staff. (2017, November 7). AboutKidsHealth. Retrieved October 31, 2020, from https://www.aboutkidshealth.ca/Article?contentid=848
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