Neural tube defects are medical conditions which occur in every 1000th live birth in the United States. Medically speaking, a neural tube defect can be characterized as an opening in the brain or the spinal cord and it always occurs in the early stages of the fetal development. The second week of pregnancy is referred to as gastrulation and it is the exact period when the neural tube gets formed when the specialized cells fuse on the dorsal side of the fetus. In case this tube does not get closed properly, it is a situation in which the harmful neural tube defects start taking place. Vitamin B12 and folic acid are very important elements when it comes to reducing the risk of different types of neural tube defects. Folate is essential in the synthesis of the DNA and RNA and the production and maintenance of all new cells in the human body. Another important role of folate is transfer of a certain carbon group so that it can be methylated and also proper synthesis of the nucleic acid. Vitamin B12 is one of the most important receptors in the biopathway of the folic acid. The exact causes of neural tube defects are largely unknown and cannot be pin pointed, but there are still certain ones which may be associated with this type of medical condition. They include maternal cigarette smoking, maternal exposure to second hand smoke, radiation, hyperthermia in early development, exposure to arsenic, mycotoxins in contaminated corn meal, maternal obesity, maternal diabetes and different sorts of folate antimetabolites.
Classification of Neural Tube Defects
All neural tube defects can be divided into two groups – closed neural tube defects and open neural tube defects. Open neural tube defects are much more common and they occur when the spinal cord or the brain get exposed at birth due to some physical defect in the back bones or the skull. The most frequent types of open neural tube defects include spina bifida, schizencephaly, iniencephaly, hydranencephally, encephaloceles and anencephaly. Closed types of neural tube defects are relatively rare and they are usually associated with certain spinal defects which are covered by skin. The most common types of closed neural tube effects include the tethered cord, lipomeningocele and lipomyelomeningocele. Spina bifida is a type of open neural tube defects and it can be divided into two subtypes known as spina bifida occulta and spina bifida cystica. Spina bifida occulta is a medical condition that affects the meninges which do not herniate through the opening in the spinal canal. In most cases, this medical condition is not considered to be harmful as it does not involve the spinal nerves or the spinal cord. Spina bifida cystic is different as it involves the presence of myelomeningocele which is characterized by herniation of the meninges and the spinal cord or meningocele which is less severe and it involves only herniation of the meninges. Iniencephally is one of the rarest types of open neural tube defects and it is triggered by extreme bending of the head to the spine. In most cases, the neck is absent, the skin of the face connected to the chest and the scalp connected to the upper back. The infant cannot survive for more than a few hours. Hydranencephaly is another type of open neural tube defect in which cerebral hemispheres are filled with sacs of cerebrospinal fluid. Anencephaly is one of the most severe types of open neural tube defects and it is characterized by a complete absence of the major part of the brain and the skull. The infant is commonly blind, unconscious and deaf.
There are certain tests which need to be conducted in order to confirm the presence of a neural tube defect. Such tests include the measurement of maternal serum alpha fetoprotein and ultrasound examination. Additional tests which may also be required in some cases include amniotic fluid acetylcholinesterase and amniotic fluid alpha fetoprotein tests.
Fortunately enough, there are certain measures which can be taken in order to prevent neural tube defects from occurring in the first place. Any pregnant woman or a woman trying to conceive needs to be well aware of the fact that folic acid supplements may prevent more than half the cases of neural tube defects. They need to be taken one month before the actual conception and all the way until the end of the first three months of pregnancy. The recommended daily dose is 400 micrograms but pregnant women should take 1000 micrograms each day. It is also strongly advised to ingest folic acid fortified foods. Women who have already experienced pregnancy with neural tube defects need to take a daily dose of 4,000 micrograms of folic acid supplements.
Most different types of neural tube defects cannot be treated at all, although survival and certain functions of infants affected by spina bifida and meningoceles may be improved by aggressive surgical management.