What is spina bifida?
Spina bifida, also called myelodysplasia, is a condition in which there is abnormal development of the back bones, spinal cord, surrounding nerves, and the fluid-filled sac that surrounds the spinal cord. This neurological condition can cause a portion of the spinal cord and the surrounding structures to develop outside, instead of inside, the body. The defect can occur anywhere along the spine.
What are the types of spina bifida?
The types of spina bifida include the following:
Spina bifida occulta - a mild form of spina bifida in which the spinal cord and the surrounding structures remain inside the baby, but the back bones in the lower back area fail to form normally. There may be a hairy patch, dimple, or birthmark over the area of the defect. Other times, there may be no abnormalities in the area.
Meningocele - a moderate form of spina bifida in which a fluid-filled sac is visible outside of the back area. The sac does not contain the spinal cord or nerves.
Myelomeningocele - a severe form of spina bifida in which the spinal cord and nerves develop outside of the body and are contained in a fluid-filled sac that is visible outside of the back area. These babies typically have weakness and loss of sensation below the defect. Problems with bowel and bladder function are also common. A majority of babies with myelomeningocele will also have hydrocephalus, a condition that causes the fluid inside of the head to build up, causing pressure inside of the head to increase and the skull bones to expand to a larger than normal size.
Approximately 80 percent of defects are found in the lower back area. The remaining 20 percent of the defects are located in the back of the neck or upper back areas.
What causes spina bifida?
Spina bifida is a type of neural tube defect. Neural tube defects, including spina bifida (open spine) and anencephaly (open skull), are seen in seven out of 10,000 live births in the US.
During pregnancy, the human brain and spine begin as a flat plate of cells, which rolls into a tube, called the neural tube. If all or part of the neural tube fails to close, leaving an opening, this is known as an open neural tube defect (or ONTD). This opening may be left exposed (80 percent of the time), or covered with bone or skin (20 percent of the time).
Anencephaly and spina bifida are the most common types of ONTD, while encephalocele (in which there is a protrusion of the brain or its coverings through the skull) is much rarer. Anencephaly occurs when the neural tube fails to close at the base of the skull, while spina bifida occurs when the neural tube fails to close somewhere along the spine.
In over 95 percent of cases, an ONTD occurs without a prior family history of these defects. ONTDs result from a combination of genes inherited from both parents, coupled with environmental factors. For this reason, ONTDs are considered multifactorial traits, meaning "many factors," both genetic and environmental, contribute to their occurrence.
Some of the environmental factors that may contribute to ONTDs include obesity, uncontrolled diabetes in the mother, and certain prescription medications. According to the Centers for Disease Control and Prevention (CDC), the occurrence rate of ONTDs can vary from state to state and from country to country.
ONTDs are seen five times more often in females than males. Once a child with an ONTD has been born in the family, the chance for an ONTD to occur again is increased to 4 percent. It is important to understand that the type of neural tube defect can differ the second time. For example, one baby could be born with anencephaly, while a second baby could have spina bifida (not anencephaly).
Prevention of neural tube defects
Because the neural tube closes 28 to 32 days after conception and before many women are aware they are pregnant, normal development of the brain and spinal cord may be affected during these first three to eight weeks of pregnancy by the following:
Exposure to hazardous chemicals/substances
Lack of proper vitamins and nutrients in the diet
Prescription drug and alcohol consumption