Neural Tube Birth Defect in Babies
During the early stages of pregnancy, the core structure that develops into the baby’s spinal cord and brain are formed. Due to some deficiencies and genetic factors, some foetuses develop these structures with some abnormality. These abnormalities stay and get magnified as defects in the brain or spinal cord. These malformations are collectively called neural tube defects (NTD). This article discusses the various aspects of this birth defect, and the precautions that expecting mothers can take to deliver a healthy baby.
What Are Neural Tube Defects?
Neural tube defects are birth defects that are characterized by abnormalities in the spine or brain of the developing foetus. It is one of the most common forms of birth defects in babies worldwide. These defects occur during the first month of the pregnancy, and are detected in the first trimester itself.
What Is a Neural Tube?
The neural tube is a flat and tiny ribbon-shaped structure that develops inside an embryo within the first few weeks of its formation. It is this primitive structure that gives rise to the brain and the spinal cord in a fully developed baby. As this structure forms the basis of the vital organs, an abnormality in its development or differentiation results in a group of defects termed as neural tube defects.
Types of Neural Tube Defects
Neural tube defects are broadly classified as open neural tube defects and closed neural tube defects, based on the whether the brain and spinal cord are covered or not. Each of these has a number of subtypes, which are discussed in detail below.
Open Type Neural Tube Defects
In the open type neural defect, the brain and the spinal cord are seen outside the skull or the vertebral column. Meningitis is commonly found to be associated with this type of defect. The open type includes conditions like spina bifida, encephaloceles, iniencephaly, and schizencephaly, hydranencephaly, and anencephaly.
1. Spina Bifida
Spina bifida is a very common type of neural tube defect that is caused when the lower part of the spinal cord protrudes out of the body. It is usually associated with damaged nerves in that region. Children with spina bifida are likely to have paralysis of the extremities, especially the leg, and poor control of urine and stool.
There are three sub-types of spina bifida, namely, spina bifida occulta, meningocele, and myelomeningocele. Spina bifida occulta is the mildest form of spina bifida, where there is a small space in the spinal cord that does not have any implications on the brain or spinal cord. Meningocele is a condition that refers to a small protrusion of the meninges in the back. Myelomeningocele is a very severe form of the neural tube defect that involves the protrusion of a small portion of the spinal cord and the surrounding tissue. It is characterised by intellectual disability caused by fluid accumulation in the brain, and complete or partial paralysis of the leg.
2. Anencephaly
Anencephaly is the abnormality of the neural tube in the upper end, causing children to be born without a portion of the brain and the skull. The remaining part of the brain is very cluttered and disorganised. Children with anencephaly are usually still born or do not survive for more than a few weeks of birth.
3. Encephalocely
During the formation of brain in the embryo, when the neural tube does not close properly, leaving a sac-like protrusion of the brain and its membrane, it is termed as encephalocele. This condition is relatively rare, and is almost always accompanied by developmental disabilities, paralysis of the upper and lower extremities, seizures, hydrocephalus, ataxia, abnormalities of the face and head, and problems wit vision. Some children who have encephalocele survive to have normal intelligence.
4. Iniencephaly
Iniencephaly is a rare form of a neural tube defect that is characterised by exceptionally large heads that are tilted backwards. It is also often associated with absence of neck, distorted spine, defective spinal cord, and cleft lip. Babies born with this disorder do not survive for long after birth.
Closed Type Neural Tube Defects
In the closed neural tube defect, the neural tissue is not visible outside. It is covered by a patch of hairy or discloured skin. In this type of neural defect, the spinal cord is attached to the tissue of the back, preventing it from growing with age. Some types of closed neural tube defects are:
1. Lipomyelomeningocele
This is a condition where a mass of fat tissue under the skin tethers itself to the back bone, preventing it from growing. It is visible as a large lump, and is often associated with poor bladder and bowel control, and weakness in the legs.
2. Lipomeningocele
Lipomeningocele is a condition where a small portion of the spinal cord protrudes out under the skin, and gets attached to the tissues in the back. The protrusion affects the nerves radiating from that part of the spinal cord, giving raise to neurological defects.
Causes
The causes of neural tube defects can be one of the following:
Genetic Factors
Neural tube defects are caused due to certain mutations in genes encoding the enzyme Methylenetetrahydrofolate reductase (MTHFR). These variations can increase the likelihood of a child being born with neural defects. A family history of tube defects also increases the chances greatly.
Folic Acid Deficiency
Folic acid, or Vitamin B9, is an absolutely vital nutrient for the proper formation of the neural tube. Expecting mothers who have a deficiency of folic acid have a higher chance of giving birth to a baby with neural tube defects. Folate plays an important role in the methylation process of the cytoskeleton, as part of the post-translational modifications. These post translational modifications are vital in giving functionality to the proteins.
Doctors usually prescribe folic acid supplements, upto 400 micrograms per day, to women in their first trimester to avoid these defects. Folic acid deficiency-associated NTD account for nearly 70% of the cases worldwide.
Uncontrolled Diabetes
If the mother has uncontrolled gestational diabetes, there are high chances for the baby to have NTD. Maternal diabetes particularly affects the gene set responsible for neural tube defects.
Weight Gain
Obesity in the expecting mother is found to be a risk factor for the occurrence of neural tube defects.
Medications During Pregnancy
Certain medicines, particularly those that are taken to control seizures, have an adverse effect of the organ formation and development of the foetus. Anti-epileptic drugs like carbamazepine and Valproate show increased risk of causing neural tube defects.
Smoking
Primary or secondary exposure to smoking increases the chances of the mother delivering a baby with NTD. The chemicals in the cigarette are likely to hamper the folate-mediated methylation process
What Is Spina Bifida?
Spina bifida is what is known as a neural tube defect. It occurs during development prior to birth. It’s when the spinal cord, brain, or meninges (their protective covering) does not completely develop. It can be anywhere along the spine and usually can be seen in an opening in the baby’s back at birth. It may also appear as a sack of fluid that has grown outside the body on the spine. This sack may or may not include the spinal cord inside.
Types of Spina Bifida
There are two forms of Spina Bifida: spina bifida occulta and spina bifida cystica.
1. Spina Bifida Occulta
Occulta is a Latin word which means ‘hidden’. In this condition, the affected area may be covered by a layer of skin, a patch of hair, etc. It has no major complications with most parents not even knowing that their child has a medical condition. This is a mild type of spina bifida. It does not cause any disabilities and may go unnoticed until later in life. There is usually no opening in the baby’s back, but only a gap in the spine. In this type, there is no damage to the spinal cord or the nerves.
2. Spina Bifida Cystica
Spina bifida cystica is characterized by the presence of a sac or a cyst, as a large blister at the back of the baby which is covered with a thin layer of skin.
Spina bifida cystica is of two types:
Myelomeningocele
A large fluid-filled sac bulges out of the baby’s back as meninges and in the spinal cord. At times, the sac bursts during childbirth exposing the spine and nerve. This is the most common and serious type of spina bifida. It involves a sack outside the opening in the baby’s back somewhere on the spine. This sack contains parts of the spinal cord and nerves. The spinal cord and nerves in the sack will be damaged.
People with myelomeningocele have physical disabilities that range from moderate to severe. These disabilities may include:
· incontinence
· difficulty going to the bathroom
· inability to move or feel their legs or feet
Meningocele
This is the rarest form of spina bifida and less serious than myelomeningocele. Babies born with this condition have a fluid-filled sac on the head, neck or back. The sac can be as large as a grapefruit or as small as a grape. Babies with this condition can have a problem controlling bowel movements and can suffer from paralysis.
Symptoms of spina bifida
The symptoms of spina bifida are different for each type. They can also vary from person to person within each type.
Myelomeningocele
Symptoms of myelomeningocele spina bifida include:
· open spinal canal over some vertebrae, usually in the middle or lower part of the back
· membranes and spinal cord pushed outside the back in an exposed or skin-covered sack
· weak or paralyzed leg muscles
· seizures
· deformed feet
· hips that are not even
· scoliosis (curved spine)
· issues with the bowel and bladder
Meningocele
Symptoms of meningocele type of spina bifida include:
· small opening in the back
· sack that’s visible at birth
· membranes pushing out through the opening in the vertebrae into sack
· normal development of the spinal cord
Membranes can be surgically removed in cases of meningocele.
Spina bifida occulta
Symptoms of spina bifida occulta include:
· a gap in between vertebrae
· no visible opening outside
· no fluid-filled sack outside the body
· small birthmark or dimple on the back
· small group or cluster of hair on the back
· an area of extra fat on the back
A person may not ever know they have this type of spina bifida.
Spina bifida in children vs. in adults
Spina bifida is not curable, so it will need to be managed your entire life.
In children
For children, treatment focuses on determining the extent of symptoms and disabilities as they develop and preventing those that can be prevented. Proper rehabilitation and medical interventions will be determined and used throughout the child’s development. Childhood is also the time for parents and medical staff to instill a positive attitude toward treatment and management to help the child develop a positive outlook.
In adults
By adulthood, the majority of symptoms and disabilities are known. Coping mechanisms, medications, therapies, and any walking aids are normally in place. Many children with spina bifida grow up to attend college and have careers. Some also live independently.
However, ongoing medical issues can develop throughout the life of a person with spina bifida. Further, some people with more severe disabilities may struggle socially due to stigma and have difficulty finding careers that will fit with their disabilities. However, a good support network can help ease the negative effects.
Treatment
The treatment for spina bifida will be different for each person because symptoms and severity can vary. In some cases, especially in spina bifida occulta, there may not be any treatment needed.
However, myelomeningocele and meningocele require surgery to put the exposed sack and nerves back in place. Some of it may also require removal. The surgeon will then close the opening over the vertebrae. There may be a shunt put in place to avoid complications later in life. This surgery may be performed shortly after the child’s birth. In some cases, prenatal surgery may be done while the baby is still in the womb. You should talk to your doctor about the benefits and risks of both types of surgery.
Even after surgery is performed, some symptoms and disability can remain. They will need to be managed based on the severity of each symptom. Paralysis and bowel and bladder issues typically remain throughout life. Treatment for remaining symptoms can include:
· additional surgeries
· medications
· physical therapy
· rehabilitation services
· walking aids
Prevention
Spina bifida occurs very early in pregnancy. Most women don’t even know they’re pregnant by the time it occurs. So if you’re trying to become pregnant, you should start taking preventive measures against spina bifida. Follow these preventive steps:
· Take a folic acid supplement as prescribed by your doctor.
· Include leafy green vegetables, nuts, beans, and other foods that contain folic acid in your diet.
· Discuss any medications or supplements you take with your doctor.
· If you have diabetes, make sure it’s under control prior to pregnancy.
· If you’re overweight, you should talk to your doctor about a healthy diet and exercise plan.
· Keep your body from overheating from saunas, hot tubs, or a fever.
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What Is Anencephaly?
Anencephaly is a birth defect in which the brain and bones of the skull don’t form completely while the baby is in the womb. As a result, the baby’s brain, particularly the cerebral cortex, develops minimally. The cerebral cortex is the part of the brain primarily responsible for thinking, movement, and senses, including touch, vision, and hearing.
Anencephaly is considered a neural tube defect. The neural tube is a narrow shaft that normally closes during fetal development and forms the brain and spinal cord. This usually happens by the fourth week of pregnancy, but if it doesn’t, the result can be anencephaly.
This incurable condition affects about three pregnancies per 10,000 in the United States each year, according to the Centers for Disease Control (CDC). In about 75 percent of cases, the baby is stillborn. Other babies born with anencephaly may only survive a few hours or days.
In many cases, a pregnancy involving a neural tube defect ends in miscarriage.
What causes it and who’s at risk?
The cause of anencephaly is generally unknown, which can be frustrating. For some babies, the cause may be related to gene or chromosome changes. In most cases, the baby’s parents have no family history of anencephaly.
A mother’s exposure to certain environmental toxins, medications, or even foods or beverages may play a role. However, researchers don’t know enough about these potential risk factors yet to provide any guidelines or warnings.
Exposure to high temperatures, whether from a sauna or hot tub or from a high fever, may raise the risk of neural tube defects.
The Cleveland Clinic suggests certain prescription drugs, including some of those used to treat diabetes, may increase the risk for anencephaly. Diabetes and obesity may be risk factors for pregnancy complications, so it’s always ideal to talk with your doctor about any chronic conditions and how they may affect your pregnancy.
One important risk factor related to anencephaly is inadequate intake of folic acid. A lack of this key nutrient may raise your risk of having a baby with other neural tube defects in addition to anencephaly, such as spina bifida. Pregnant women can minimize this risk with folic acid supplements or diet changes.
If you’ve had an infant with anencephaly, your chance of having a second baby with the same condition or a different neural tube defect increases by 4 to 10 percent. Two previous pregnancies affected by anencephaly increase the recurrence rate to about 10 to 13 percent.
How is it diagnosed?
Doctors can diagnose anencephaly during pregnancy or immediately after the baby is born. At birth, the abnormalities of the skull can be easily seen. In some cases, part of the scalp is missing, along with the skull.
Prenatal tests for anencephaly include:
· Blood test. High levels of the liver protein alpha-fetoprotein can indicate anencephaly.
· Amniocentesis. Fluid withdrawn from the amniotic sac surrounding the fetus can be studied to search for several markers of abnormal development. High levels of alpha-fetoprotein and acetylcholinesterase are associated with neural tube defects.
· Ultrasound. High-frequency sound waves can help create images (sonograms) of the developing fetus on a computer screen. A sonogram may show the physical signs of anencephaly.
· Fetal MRI scan. A magnetic field and radio waves produce images of the fetus. A fetal MRI scan provides more detailed pictures than an ultrasound.
The Cleveland Clinic suggests prenatal testing for anencephaly between the 14th and 18th weeks of pregnancy. The fetal MRI scan take place any time.
What are the symptoms?
The most noticeable signs of anencephaly are the missing parts of the skull, which are usually the bones in the back of the head. Some bones on the sides or front of the skull may also be missing or poorly formed. The brain also isn’t formed properly. Without a healthy cerebral cortex, a person can’t survive
Other signs may include a folding of the ears, a cleft palate, and poor reflexes. Some infants born with anencephaly also have heart defects.
How is it treated?
There is no treatment or cure for anencephaly. An infant born with the condition should be kept warm and comfortable. If any parts of the scalp are missing, exposed parts of the brain should be covered.
The life expectancy of an infant born with anencephaly is no more than a few days, more likely a few hours.
Anencephaly vs. microcephaly
Anencephaly is one of several conditions known as cephalic disorders. They’re all related to problems with the development of the nervous system.
One disorder similar to anencephaly in some ways is microcephaly. A baby born with this condition has a smaller-than-normal head circumference.
Unlike anencephaly, which is apparent at birth, microcephaly may or may not be present at birth. It can develop within the first few years of life.
A child with microcephaly may experience normal maturing of the face and other parts of the body, while the head remains small. Someone with microcephaly may be developmentally delayed and face a shorter lifespan than someone without a cephalic condition.
