A neural tube defect (NTD) is a specific type of defect that occurs in the first month of pregnancy and impacts the brain, spine or spinal cord of the developing fetus. Though neural tube defects can occur in any infant, they tend to be more common in females than in males.

There are two main types of neural tube defects – spina bifida and anencephaly. 

  • Spina bifida is a condition in which the fetal spinal column doesn’t develop properly or close completely.
  • Anencephaly is a condition in which the brain and skull fail to fully develop. Infants born with anencephaly have a very proof prognosis and are usually stillborn or die soon after birth. 

Neural tube defects pathophysiology

Neural tubes are formed in weeks 3 and 4 of embryonic development. They begin as a neural plate and finish as a neural tube. The neural tube makes up the embryo’s central nervous system, brain and spinal cord. The transition from neural plate to neural tube requires the developing embryo to go through specific steps called neurulation.  Any deviation from the neurulation process can lead to neural tube defects. 

The three layers of the embryo are the ectoderm, mesoderm and endoderm. 

  • Ectoderm – Becomes the nervous system and the epidermis. The neural plate comes from this layer
  • Mesoderm: – This layer develops into the musculoskeletal system, the urogenital system, the pleura and the body’s peritoneal linings
  • Endoderm – This layer lines the airways and GI tract

By the end of the third week of development, the ectoderm begins to form into neural folds. These folds form neural grooves which make up the neural plate. The neural plate then divides into two sections – the upper section is cranial and the lower section is caudal. These two sections begin to pull away from one another and ultimately form a long singular neural tube. 

By the end of week 4 the neural tube separates from the ectoderm, which completes its formation. As the embryo continues to develop, the cranial and caudal portions of the neural tube form the brain and spinal cord. 

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Who is most at risk for this disease?

The cause of NTDs is not fully understood, and studies suggest genetics may play a significant role. Other possible factors that could increase risk for NTDs include folate deficiency, poorly controlled diabetes, anti-seizure medications, obesity, opioid use in the first 8 weeks of pregnancy, and an elevated body temperature early in pregnancy. Additionally, a study from 2018 showed that women with HIV who were taking antiretroviral therapy (ART) that included the medication dolutegravir had a much higher incidence of neural tube defects when compared to women who did not utilize that specific drug as part of their ART.

How can neural tube defects be prevented?

Because folate (Vitamin B9) is essential for proper neural tube development and closure, one of the best ways to prevent NTDs is for the expectant individual to supplement their diet with folate or folic acid. The recommendation is to take a vitamin supplement with 400 mcg of folic acid daily in the month prior to becoming pregnant and throughout the first 12 weeks of pregnancy. 

Examples of foods high in folate (Vit B9) include legumes, leafy greens, eggs, broccoli, and citrus as well as fortified breads, grains, and cereals. 

However, it’s important to note that, though rare, some cases of spina bifida are caused by a lack of folate being transferred to the embryo, even when mom has adequate folate levels. An individual who has already had one pregnancy with a NTD is at higher risk for this complication in future pregnancies due to higher activity of certain antibodies that affect the folic acid receptor. 

Alcoholism and digestive disorders can decrease a person's ability to absorb folate.

Complications of neural tube defects

Anencephaly typically leads to death and individuals with spina bifida can have lifelong  complications including paralysis, bowel and bladder dysfunction, and lower extremity weakness. Children with hydrocephalus, which can occur with spina bifida, are at risk for developmental delays, seizure disorder, balance/coordination challenges, and other neurological problems. As a reminder, hydrocephalus is a condition of having too much fluid in the cranium due to CSF not draining properly. This condition requires surgical intervention and lifelong monitoring.

L: How does the patient LOOK?

The signs and symptoms of  a NTD will vary depending on which type the infant has.

  • Anencephaly is obvious at birth as the infant is missing parts of the skull, scalp and brain. 
  • Spina bifida can take different forms: 
    • Myelomeningocele (MY-eh-lo-men-IN-go-seal.) is the most severe form of spina bifida. In this form, a sac with fluid and nerves of the spinal cord protrudes through the baby’s spine and can be seen externally. This form of spina bifida causes moderate to severe disabilities such as bowel and bladder problems, loss of sensation, and paralysis. Generally, the higher up the protrusion occurs, the more disability the child will have.
    • Meningocele involves a sac of fluid protruding from the baby’s spine – it does not contain any nerves from the spinal cord. Because the nerves are not affected, long term impacts are minor and the prognosis is considered excellent with a simple surgical repair.
    • Spina bifida occulta involves a small gap in the spine with no protrusion of a sac or nerves outside the body. This type of spina bifida often goes unnoticed until late childhood or early adulthood and does not tend to cause any lasting disabilities. In some cases there is an external dimple or depression and a tuft of hair or a birthmark.

Another common manifestation of NTDs is hydrocephalus, which is noted by an unusually large head or rapid increase in head size, vomiting, headache, sleepiness and even seizures.

A: How do you ASSESS an infant with a neural tube defect?

How you care for the patient will be determined by the severity of the NTD and which type of defect is present. Conduct a thorough newborn assessment and with any age child, make  note of things like range of motion, sensory perception, and functional ability relevant to the child’s age. Specific assessments include: 

  • Observe for a visible defect on the infant’s back, which could be as simple as a dimple and tuft of hair or a fluid filled sac that may or may not contain components of the spinal cord.
  • If a sac is present, assess the sac for leakage of CSF, redness and irritation. Also assess the skin around the sac and make note of purulent drainage which indicates infection.
  • Assess for numbness or loss of sensation in the lower extremities. In infants and young children, this may involve irritating or painful stimuli such as performing a heel stick and noting a response. An infant who does not react to painful stimulation will need further evaluation by a neurologist.
  • Evaluate the child for paralysis or weakness in the lower extremities as well as any difficulties with walking (including the use of assistive devices).
  • Assess for bowel and bladder dysfunction, as appropriate for the child’s age. For example, a 14 month old baby is expected to be incontinent, but an eight year old child is not. Additionally, some children can have neurogenic bladder and may require catheterization for adequate emptying.
  • Assess the child for developmental delays that could require further assessment with a validated tool such as the DAYC-2 screening tool. This assessment is used to identify delays in five key areas – cognition, communication, social-emotional development, physical development, and adaptive behavior.
  • Ask the parent about latex sensitivity, which is common in children with spina bifida.
  • Asses the child for hearing loss and visual impairment.
  • Measure the child’s cranium and assess for hydrocephalus, which causes increased head size, nausea, headache, sleepiness and seizures.

T: What TESTS will be conducted for a child with a neural tube defect?

Many diagnostic tests for a neural tube defect are conducted during pregnancy and include:

  • AFP levels – Elevated maternal alpha fetoprotein levels in the maternal serum and the amniotic fluid indicate that CNS abnormalities are probable. AFP levels are often obtained through the “triple screen” and “quad screen” which evaluate AFP levels as well as hCG, estriol and inhibin-A. These tests are generally conducted between the 15th and 20th week of pregnancy.
  • Maternal serum FOLR1: Serum folate receptor alpha (FOLR1) is elevated in pregnancies that involve a NTD. 
  • Ultrasonography – An ultrasound of the fetus could show an incomplete neural tube.
  • Fetal MRI – This imaging test can show abnormalities and be conducted as early as 20 weeks. 
  • Other imaging studies may be conducted after the child is born- Additional evaluation of the defect may include magnetic resonance imaging (MRI), computed tomography (CT), and myelography. 

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T: What TREATMENTS are provided for neural tube defects? 

Surgery – The key treatment for a myelomeningocele is surgery to close the opening and repair the spinal cord. Surgery may be performed prenatally prior to the 26th week of pregnancy or within 72 hours after birth. Research shows that children who receive prenatal surgery have better outcomes with reduced disability when compared to children who have the surgery after birth. Some children require multiple surgeries to repair the defect. Meningocele is also surgically treated and involves closing the opening to prevent infection and protect the exposed portion of the baby’s spine.

Note that many infants with spina bifida are still at an elevated risk for hydrocephalus and skull malformations that press the brain down toward the spinal canal. Additional surgical procedures will be utilized as needed.

Ventriculoperitoneal (VP) shunt – Since many children with NTDs also have hydrocephalus, a VP shunt may be surgically placed to help facilitate drainage of CSF and reduce intracranial pressure. 

Cesarean birth – Many babies with NTDs are in the breech position and a c-section is often deemed a safer alternative for babies with an exposed sac.

Infection prevention – Infants with myelomeningocele and meningocele are at high risk for nervous system infection and meningitis. The sac should be covered with a sterile moist dressing and changed every two hours to ensure the sac does not dry out and break. The dressing may be covered in a plastic film to prevent cross contamination from urine or stool. Once surgery has occurred, maintain a clean, dry surgical dressing.

Preserve skin integrity – Ensure the area is kept clean, dry, and free of urine and stool. If diapers are worn, ensure they don’t rub against the affected area. If the defect is low on the spine, diapers are not recommended.

Ensure proper positioning – Maintain the infant in a prone position to avoid putting pressure on the sac.

Addressing complications – Long-term complications of spina bifida will be addressed depending on the child’s specific needs. This can include walking and mobility aids, therapies aimed to address bowel and bladder dysfunction, and treatments for orthopedic complications, skin issues and gastrointestinal problems. For example, many children with spina bifida require catheterization to fully empty their bladders as well as medications such as oxybutynin which treats bladder spasms.

Assume latex allergy – Many children with spina bifida develop latex allergy. To be on the safe side, utilize latex free medical supplies with all individuals who have spina bifida. Common items that contain latex include indwelling catheters, glue, tourniquets, gloves, and even balloons.

PT, OT, SLP – Depending on the child’s disabilities, additional therapies may be utilized including physical therapy, occupational therapy, and speech therapy.

Note that there are no medical treatments for anencephaly since the majority of newborns with this condition are born stillborn due to their lack of brain development, while others typically die within hours of birth. The focus for these patients is emotional support for the families.

E: How do you EDUCATE the family?

A key component of your family education is assessing their understanding of their child’s condition and readiness to learn. In the immediate period following the birth, teach parents infection prevention measures as well as how to hold and position their infant so as to not damage or irritate the sac. Other important teaching includes: 

  • Ensure parents understand how and when to administer any medications
  • Ensure parents are familiar with their child’s various therapies and the benefits of each
  • Teach parents how to perform ROM exercises (or reinforce teaching provided by the physical therapist).
  • Teach parents to avoid latex, which can be in a wide range of household items including bandages, pacifiers and balloons.
  • Teach parents the signs of latex allergy – coughing, itchy and watery eyes, rash, and sneezing. Ensure parents understand to seek immediate medical care if the child has difficulty breathing, hives, swelling of the face, lips, neck or tongue, difficulty swallowing, or feelings of fullness in the throat.
  • If the parents are planning on having additional children, teach them to take a folate supplement prior to attempting to conceive and throughout pregnancy.

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You can review neural tube defects again while you’re on the go in episode 315 of the Straight A Nursing podcast. Tune in wherever you get your podcast fix, or straight from the website here.

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