Definition

Neural Tube Defects (NTD) are the result of the neural tube failing to form or close properly during embryonic development.

Clinical signs

The individual neural tube defects each have their own unique signs and etiology.

Etiology

The brain and spinal cord begin development as a groove that folds over laterally to become a tube (the neural tube). Layers of tissue that come from this tube normally cover the brain and spinal cord (meninges).

Fusion of the neural tube begins cranially (towards the head) and progresses caudally (towards the tail). The anterior and posterior ends of the neural tube remain open for a period of time during neural tube development, but eventually close.

In NTDs the neural tube does not develop normally, which may affect the brain, spinal cord, and meninges.

Some Examples of Neural Tube Disorders

• Anencephaly-
  • Anencephaly is the most severe form of neural tube defect, the brain tissue as well as a portion of the spinal cord are absent. This defect is fatal.

• Spina Bifida-
  • The term spina bifida covers a range of vertebral and neural tube defects.
    Spina bifida results when the neural tube fails to close completely and remains an open channel. It is the failure of the posterior vertebral arch to fuse.

• Exencephaly-
  • A condition in which the skull has not developed normally, causing exposure or extrusion of the brain.

• Hydrocephaly-
  • Hydrocephally is an abnormal accumulation of cerebrospinal fluid in the ventricles of the brain resulting in elevated intracranial pressure. It is often referred to as “water on the brain.”

Neural Tube Development

• Fig. 1: Diagram of normal neural tube development

Specific Neural Tube Disorder Articles and Examples

Anencephaly article

Hydrocephaly article

Diagnostics

Diagnosis of NTD can be very obvious or go undetected. The individual NTDs each have their own unique signs that lead to diagnosing the type of defect. Some can be determined visually, while others will be better diagnosed using X-rays, scans, or during necropsy.

Treatment

Treatment, or lack of treatment will depend on the type of NTD that you are dealing with. Treatment, if called for, can range anywhere from no treatment, to veterinary care, surgery, home nursing care, or euthanasia.

Prevention of Neural Tube Defects

Studies have indicated that the following causes may be contributory factors in the development of Neural tube defects:

• Genetic: it is possible for this condition to have hereditary factors
• Nutritional: an absence of folic acid or the inability to store or process folic acid
• Environmental: toxins, maternal infections, antimicrobial treatment, or hypothermia during pregnancy

Not all neural tube defects can be prevented. When it is determined that there are hereditary factors involved, choosing not to breed from lines with NTDs will reduce the chances of producing more rats with these disorders.

Folic acid, also known as folate or folacin, is a B-complex vitamin that is needed for correct neural tube development. Research has shown that the addition of folic acid to the mothers diet prior to and during gestation may reduce the number and/or severity of NTDs.

Folate can be found naturally in the following foods:

• Dried beans
• Legumes
• Lentils
• Peanuts and sunflower seeds
• Leafy greens (romaine lettuce, spinach)
• Broccoli
• Oranges, strawberries, melon
• Chicken liver (very high in folic acid)

Sources of supplemental folic acid:

• Fortified cereals (Total, Product 19)
• Whole wheat products
• Pasta (fortified)

*Note: Folic acid is the synthetic form of folate and is actually absorbed by the body better. You will find folic acid in fortified foods or vitamin supplements as opposed to natural foods.

References

1. Embryonic development of the nervous system. (2005, February 1). Retrieved December 18, 2008, from https://www.niaaa.nih.gov/Resources/GraphicsGallery/FetalAlcoholSyndrome/Embryonic.htm.
2. Folic Acid. (n.d.). Retrieved December 18, 2008, from http://www.marchofdimes.com/professionals/14332_1151.asp.