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 85 percent of defects are found in the lower back area. The remaining 15 percent of the defects are located in the back of the neck or upper back areas.

Spina bifida is one of the most common severe birth defects, historically occurring in 1 live birth per 1000 in the United States. The rates of spina bifida are higher in Hispanics and whites of European descent than in Ashkenazi Jews, Asians, and African Americans.

Rates are also higher among mothers with certain health problems, such as diabetes or seizure disorders (taking certain anticonvulsants), and significantly higher among couples in which at least one has spina bifida, and among couples who have already had a child with spina bifida.

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 one to two out of 1,000 live births.

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 90 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 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. The rate of ONTD occurrence in Arkansas is 7.8 out of 10,000 births and 30 out of 10,000 births in Washington. Ireland has the highest number of documented cases, where spina bifida occurs in approximately 4.2 out of 1,000 live births. The factors causing these differences are not well understood.

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 3 to 5 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).