Definition

Anencephaly is congenital neural tube birth disorder (NTD) that causes the absence of a major portion of the brain, skull, and scalp.

Clinical signs

A pup born with anencephaly has a very distinctive appearance. At first glance you will notice that a portion of the skull and scalp is missing exposing an underdeveloped/incomplete brain.

Anencephalic babies are usually stillborn, although some may survive for a short time after birth.

Signs of anencephaly include the following:

• Absence of a portion of the skull (calvarium), the membranous layers of connective tissue that envelop the brain and spinal cord (meninges), and scalp.
• Brain exposure with only a partial covering of membrane.
• Brain is poorly developed and not functional (rudimentary).
• Both cerebral hemispheres may be missing.
• Cerebellum is absent.
• The cranial defect may descend to the cervical area exposing the spinal cord (craniorachischisis).
• May see protrusion of the eyes or other anomalies.

Etiology

Anencephaly is a neural tube defect (a disorder involving incomplete development of the brain, spinal cord, and/or their protective coverings) seen in rats as well as other species. In rats this affliction seems to be very rare.

During embryonic development the neural tube develops and closes to form the brain as well as the spinal cord. Anencephaly occurs when the anterior end of the neural tube does not close. This results in the absence of a portion of the brain, the skull, and the scalp. Anencephaly occurs when the cephalic (closer to the head) end of the neural tube fails to close. Often the cause of the defect can not be determined. It can be, although isn’t necessarily, an issue of heredity.

Studies have indicated that the following causes may be contributory factors in the development of anencephaly:

• 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

Photos and case histories of hydrocephalus

• Fig. 1: Anencephaly photos and case history. *Warning! These photos are very graphic in nature.

Diagnostics

Anencephaly is usually diagnosed visually after birth as mentioned above in the “Clinical Signs” section of this article. Further issues can be addressed via necropsy.

Pathology

• Underdeveloped (hypoplastic) pituitary gland
• Brain stem residue usually present

Treatment

There is no treatment for anencephaly. In most cases, babies will either be stillborn or die shortly after birth. Humane euthanasia, if the pup is born alive, may be the only option. Your vet can help you decide the proper course of action.

Outcome

At this time there is no documentation of rat babies born with anencephaly surviving.

Prevention

In order to help prevent this condition from showing up in a litter, breeders need to be aware of any predisposing genetic traits in their colonies.

Folic Acid/Folate

Folic acid, also known as folate or folacin, is a B-complex vitamin that is needed for correct neural tube development.

Folate refers to the form of this vitamin found naturally occurring in foods. Folic acid is the synthetic form of the B vitamin.

Folic acid in the diet of breeding females may lessen or alleviate incidents of neural tube development disorders such as anencephaly, spina-bifida. Because NTDs (neural tube disorders) happen very early in embryonic development it is suggested to supplement the mother with foods rich in folic acid before breeding her as well as throughout the pregnancy.

Folate can be found naturally in the following foods:

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

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.
Sources of supplemental folic acid:

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

References

1. Anencephaly Information Page. (n.d.). Retrieved December 18, 2008, from http://www.ninds.nih.gov/disorders/anencephaly/anencephaly.htm.
2. Anencephaly. (n.d.). Retrieved December 18, 2008, from http://www.angelfire.com/mn/michaelashope/anencephalyfact.html.
3. Anencephaly. (n.d.). Retrieved December 18, 2008, from http://en.wikipedia.org/wiki/Anencephaly.
4. Brooks, E. (n.d.). SRR Anencephaly Page (Case History). Retrieved December 18, 2008, from http://www.spoiledratten.com/rascalxginnie.html.
5. Folate (Folacin, Folic Acid). (n.d.). Retrieved December 18, 2008, from http://ohioline.osu.edu/hyg-fact/5000/5553.html.
6. Folic Acid. (n.d.). Retrieved December 18, 2008, from http://www.marchofdimes.com/professionals/14332_1151.asp.