PCL 12- What is Spina Bifida and Pathopysiology.

What is Spina Bifida?
Spina bifida means ‘split spine’. It is a developmental birth defect due to the incomplete closure of the embryonic neural tube.
Some vertebrae that overly the spinal cord does not form completely and remain unfused and open, allowing portions of the spinal cord to protrude through. There may be a fluid-filled sac surrounding the spinal cord, but NOT always
Other neural tube defects include:
- anencephaly , a condition in which the portion of the neural tube which becomes the cerebrum does not close, and
- encephalocele, which results when other parts of the brain remain unfused.
Spina bifida malformations fall into four categories:
- spina bifida occulta: the outer part of some of the vertebrae are not completely closed. The split in the vertebrae is so small that the spinal cord does not protrude. The most mildest form.
- spina bifida cystica (myelomeningocele): a cyst protrudes through the defect in the vertebral arch
-meningocele: least common form of spina bifida is a posterior meningocele. In a posterior meningocele, the vertebrae develop normally, however the meninges are forced into the gaps between the vertebrae.
-lipomeningocele: An intraspinal lipoma associated with spina bifida.
The most common location of the malformations is the lumbar and sacral areas.

Myelomeningocele:
A serious and common form, the unfused portion of the spinal column allows the spinal cord to protrude through an opening. The meningeal membranes that cover the spinal cord form a sac enclosing the spinal elements.
The protruded portion of the spinal cord and the nerves which originate at that level of the cord are damaged or not properly developed. As a result, there is usually some degree of paralysis and loss of sensation below the level of the spinal cord defect. Thus, the higher the level of the defect the more severe the associated nerve dysfunction and resultant paralysis.

Pathophysiology
Spina bifida occurs at the end of the first month of pregnancy ( around 28 days after conception) when the two sides of the embryo's spine fail to join together.
Myelomeningocele, the most common type of spinal dysraphism compatible with life, occurs with an incidence of 1 in every 1200 to 1400 live births. It is due to a local failure of neural tube closure during primary neuralation. Fusion of the lateral cutaneous ectoderm and the process of disjunction also fail to occur in myelomeningocele, resulting in a midline cutaneous defect over exposed neural tissue called the neural placode. Therefore, myelomeningoceles are considered open neural tube defects.
Research has shown that lack of folic acid(folate) is a contributing factor in the pathogenesis of neural tube defects, including spina bifida. Supplementation of the mother's diet with folate can reduce the incidence of neural tube defects by about 70 percent, and can also decrease the severity of these defects when they occur. It is unknown how or why folic acid has this effect. As a result of this finding, the U.S. Federal Drug Administration mandated that cereal grains sold in this country be fortified with at least 140 mcg of folic acid per 100 grams of grain by January 1, 1998.
Also, Researchers have discovered an association between genes regulating glucose metabolism and spina bifida. The 10 year study looked at more than 1,500 DNA samples from parents and their children with that birth defect.It has been recognized through epidemiological studies for a number of years that there was a connection between high glucose levels, either due to maternal diabetes or obesity and having a child with spina bifida