Neural Tube Defects: Causes, Types, Treatment & More

Introduction

The first three months of pregnancy are crucial as it is the time when organ formation takes place. It has been observed that many birth defects happen during the first 3 months of pregnancy.² Neural tube defect is one of these defects. Globally, there are more than 3,00,000 newborns every year diagnosed with neural tube defects.³ Neural tube defects are birth defects present in the brain and the spinal cord. This defect is linked to the deficiency of folic acid (vitamin B9). Development of the brain and spine begins in the first month of pregnancy. At this stage, the developing brain and spine are called the neural tube.^4-6 This defect occurs when the tube does not close completely along its length. Types of neural tube defects: Spinal bifida, Anencephaly, Encephalocele, and Iniencephaly. Spina bifida and anencephaly are more commonly reported in newborns.^3,4 Foetus detected with iniencephaly, and anencephaly die shortly after birth or die before birth or during the delivery. ⁴

Signs And Symptoms Of Neural Tube Defects

Since this neural tube defect occurs in the first month of pregnancy, the mother might not experience any signs and symptoms. During her regular ultrasound, the gynaecologist would possibly reveal signs of this type of birth defect. Following are the general symptoms that might be seen in babies with neural tube defects:

• Paralysis
• Urinary and bowel movement problems
• Blindness
• Lack of hearing (partial or complete deafness)
• Cognitive disability
• Lack of alertness⁴

When To See A Doctor

Defects in the neural tube are incurable. Normal persistent nerve damage and loss of function are evident at birth.⁷  If your child has a neural tube defect, you will probably need to see their doctor or group of doctors on a frequent basis for the rest of their lives. This defect can only be avoided not treated. So, knowledge of risk factors and causes is also very crucial. ⁴

Causes Of Neural Tube Defects

Although it is proposed that genetic reasons, nutritional deficiencies, and environmental factors all play a role in causing neural tube defects, most importantly: ⁴

• Folic acid is vital for the healthy development of the foetus. Just like any other vitamin, vitamin B9 i.e., folic acid levels are extremely crucial during pregnancy. 
• Low levels of folic acid in females before getting pregnant or during the early stages of pregnancy can result in this type of birth defect (congenital problems).

Risk Factors For Neural Tube Defects

The exact causes of neural tube defect are still under research, therefore, a female who is expecting a child should avoid or reduce the following risk factors:

• If the mother has a folic acid deficiency
• If the mother is obese
• If she has uncontrolled diabetes
• If she is on anti-seizure pills or consumes opioids^4,7
• If there is any family history of neural tube defects 
• If she has chronic unexplained hyperthermia (increased body temperature)⁴

Diagnosis Of Neural Tube Defects

The ultrasound technique is employed for detecting any abnormalities in the growing foetus. The doctor might require supporting tests to be carried out for coming to a diagnosis. The following test is a part of the examination during the pregnancy: 

• Triple screen test/Blood test: Following are the three markers checked during pregnancy to know the status of the pregnancy. 
• Alpha-fetoprotein (AFP) is a protein that the foetus makes in the womb. It is quantified during the 16^th to 18^th week of pregnancy. If AFP protein is found to be higher than the normal limit, then the likelihood of developing this defect of the neural tube is also high.^4,8
• HCG (human chorionic gonadotropin) hormone is released by the placenta during the 1^st eight weeks of pregnancy. Its levels are found to be normal in neural tube defect case.⁹
• Estriol is an oestrogen-like hormone released by the foetus and the placenta. Low levels of estriol are helpful in detecting Down’s syndrome.^6,8,9
• Prenatal ultrasound: Getting an ultrasound done during the 11^th to 14^th week of pregnancy is required by the doctor to diagnose any type of neural tube defect in the fetus.⁴
• Amniocentesis: Amniotic sac enveloping the foetus and the fluid surrounding the foetus acts as one of the methods to diagnose any birth defects. Using a needle small amount of amniotic sac fluid is withdrawn and studied. This test is conducted during the 15^th to 20^th week of pregnancy.⁴

Treatment Of Neural Tube Defects

Amongst the four types of neural tube defects, there is no treatment for infants with anencephaly or iniencephaly. Spina bifida and encephalocele can still be treated through surgical procedures depending upon the severity of the defects.

The doctor performs one or more surgeries to align the parts and membrane of the brain back into the skull. Sometimes, more than one surgery is required based on the complications.⁴ 

Prevention Of Neural Tube Defects

Neural tube defects can be prevented by lowering the risk factors during the early stages of pregnancy. 

Taking vitamin B9 supplements as prescribed by the doctor can prevent most neural tube defects.⁷  

Complications Of Neural Tube Defects

Complications associated with this type of defect are very critical and life-threatening. Following is a list of complications that may arise in an infant who is suffering from neural tube defects: ¹⁰

Complications that can occur in the mother when neural tube defect is diagnosed:

• Miscarriage and abortion: A mother might face the complication of spontaneous abortion due to a severe neural tube defect detected in the foetus. 

Complications in the baby (can be of 3 types):

A baby is at risk of facing complications at three stages i.e., when it is inside the mother’s womb, when the baby takes birth, and at the infant stage.  

1. Complications in foetus in the womb

• Polyhydraminos: When amniotic fluid accumulates in the amniotic sac due to absence of swallowing activity. Such babies with neural tube abnormalities have learning disabilities because of the restricted growth of brain tissue. About 50% of patients experience the development of polyhydraminos throughout the second and third trimesters.

2. Complications in the newborn baby

• Arnold-Chiari Malformation: It is described as a downward movement of a portion of the brain into the foramen magnum as a result of the spinal cord’s improper development.

3. Complications in the infant and later stages of life

• Meningitis: Brain’s fluid continuously oozes out which makes such babies susceptible to infection in the meninges (meninges form a protective layer over the brain).
• Intellectual disability: The healthy development of the brain depends on the fluid circulating in the brain. Despite having a normal head size, patients with such defects have reduced cortical development and therefore, reduced intellectual abilities. 

Research Facts About Neural Tube Defects

• More than 150,000 neural tube defects can be prevented with supplementation of diet  with folic acid during pregnancy.³
• Every woman planning to conceive should consume folic acid daily.¹¹ A proper consultation with a gynaecologist or any other healthcare provider should be done prior to consuming any medication during pregnancy.

Frequently Asked Questions (FAQs)

References:

1. Neural Tube Defects (NTDs): What They Are, Causes & Prevention [Internet]. Available from: https://my.clevelandclinic.org/health/diseases/22656-neural-tube-defects-ntd
2. Embryology, Neural Tube – StatPearls – NCBI Bookshelf [Internet]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK542285/
3. Neural Tube Defects | MedlinePlus [Internet]. Available from: https://medlineplus.gov/neuraltubedefects.html
4. Alpha-Fetoprotein (AFP) Test: MedlinePlus Medical Test [Internet]. Available from: https://medlineplus.gov/lab-tests/alpha-fetoprotein-afp-test/
5. Maternal Serum Triple Analyte Screening in Pregnancy | AAFP [Internet]. Available from: https://www.aafp.org/pubs/afp/issues/2002/0301/p915.html
6. Neural Tube Disorders – StatPearls – NCBI Bookshelf [Internet]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK555903/

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