Neural tube defects are serious birth defects caused by the incomplete closure of the neural tube very early in pregnancy. By definition, the neural tube is a bundle of nerves or a thin sheath that eventually closes to form the brain at its anterior end and spinal cord at its posterior end. This closure should occur around the 28th day after conception, failing which parts of the brain or spinal cord do not form properly and fail to function.
The most common forms of NTDs or neural tube defects are spina bifida, characterized by incomplete development of spine, brain and/or meninges and anencephaly, characterized by absence of a major portion of the brain, skull or scalp.
Symptoms And Complications Of Spina Bifida
Severity of this defect varies from individual to individual, with no visible signs in some mild cases to part of the spinal cord being perpetually exposed in extreme cases.
Complications of this defect can range from minor physical problems to severe paralysis and mental disabilities. Nerve damage is prominent in all those located below the site of malformation. Therefore, higher the malformation on the spine, greater the amount of nerve damage and loss of muscle function. In another associated rare malformation, Chiari II, the rear portion of the brain protrudes into the spinal canal causing depression of the spinal cord. This leads to variety of symptoms including difficulties with feeding, swallowing, and breathing; choking; and arm stiffness. Additional problems such as latex allergies, skin problems, gastrointestinal conditions, and depression may occur, as children with spina bifida get older.
Symptoms And Complications Of Anencephaly
This is a very severe defect, with infants being born without a forebrain and cerebrum, essential for thinking and co-ordinating activities. Such infants are born deaf, blind, feel no pain and are permanently unconscious due to absence of cerebrum. Prognoses for anencephaly are very poor with majority of infants being still born, or die within a few hours or days after birth.
Detection of NTDs
Prenatal screening done between 16-20 weeks often spots any neural tube disorders. Blood level of a protein, alpha fetoprotein (AFP) is checked for in maternal serum. This protein is produced naturally by the foetus and placenta with a little amount escaping into mother’s bloodstream. If abnormal amount are detected, it may indicate a neural tube defect. However, doctors may request additional testing such as foetal ultrasound and amniocentesis to further confirm the diagnosis.
Prevention of NTDs
Women who have children affected by spina bifida, or those who have the disorder themselves, or have had a previous failed pregnancy due to NTD, are at greater risk of having another child with such a defect. However, statistics also show that around 95% of couples with no family history have children affected by neural tube defects. There is no known definitive cause for this disorder, but scientists have linked the inadequate consumption of a B vitamin, folic acid, to improper closure of the neural tube.
Consumption of folic acid before conception has been shown to reduce occurrence of NTDs and is therefore prescribed by doctors in the form of prenatal vitamins. It is recommended that women pregnant for the first time should consume 400 mcg everyday and those with a history should take about five mg a day. Apart from vitamins, one should have green leafy vegetables, bread and cereals as a diet rich in folic acid.
Unfortunately, neural tube defect such as spina bifida can only be managed but not cured. Such children will require constant treatment form a multi disciplinary team to attend to any associated physical, mental, hearing and visual disabilities. Open defects should be closed promptly and in some cases, foetal surgery in utero is performed. This involves sewing shut the opening in the spinal cord while the baby is in the mother’s womb. This however involves risk to both mother and the foetus and therefore still performed with caution. With such serious consequences, the best practice than can be adopted by expectant mothers is to prevent such defects by taking adequate folic acid and nutritional care.
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