About Spina Bifida

Incidence

Approximately 40% of all Americans may have spina bifida occulta, but because they experience little or no symptoms, very few of them ever know that they have it. The other two types of spina bifida, meningocele and myelomeningocele, are known collectively as "spina bifida manifesta," and occur in approximately one out of every thousand births. Of these infants born with "spina bifida manifesta," about 4% have the meningocele form, while about 96% have myelomeningocele form.

Characteristics

The effects of myelomeningocele, the most serious form of spina bifida, may include muscle weakness or paralysis below the area of the spine where the incomplete closure (or cleft) occurs, loss of sensation below the cleft, and loss of bowel and bladder control. In addition, fluid may build up and cause an accumulation of fluid in the brain (a condition known as hydrocephalus).

Shunt

A large percentage (70%-90%) of children born with myelomeningocele have hydrocephalus. Hydrocephalus is controlled by a surgical procedure called "shunting," which relieves the fluid buildup in the brain. If a drain (shunt) is not implanted, the pressure buildup can cause brain damage, seizures or blindness. Hydrocephalus may occur without spina bifida, but the two conditions often occur together.

How Does it Happen ?

Spina bifida occurs in the first month of pregnancy, often before the woman knows that she is pregnant. Presently the exact causes of spina bifida are unknown. It is thought that there are both environmental and genetic triggers. By genetic, we do not mean hereditary in the general sense of the term. Spina bifida does not follow direct patterns of heredity like muscular dystrophy or haemophilia, but it is thought to be familial. That is, the genetic influence is expressed by an increased risk of having a child with spina bifida after having a first child with this problem, or if a close relative has a child with spina bifida (predisposition or 'familial link').

It is known that women taking medication for epilepsy have a higher chance of having a child with a neural tube defect. Genetic counselors can discuss the risk for each family member. (Contact the Spina Bifida Association for more information.)

There have been reports in the media of a connection between Agent Orange and spina bifida. In the United States an independent review of all available data on the effect of herbicide exposure has been reported. The report found "limited or suggestive evidence" that herbicide exposure in the parents could be associated with spina bifida in their children. Included in the review were a few studies of Vietnam veterans, and some of these suggest the possibility of a slightly elevated rate of spina bifida in the children of Vietnam veterans.