Anencephaly

Anencephaly is the absence of a large portion of the brain, skull, and scalp during embryonic development. It is an acephalic disorder caused by a neural tube defect that occurs when the rostral (head) end of the neural tube fails to close, usually between the 23rd and 26th day after conception. Strictly speaking, the Greek term translates as "no in-head" (that is, completely lacking the inside part of the head, i.e. the brain), but it is accepted that children born with this disorder usually only lack atelencephalon, the largest part of the brain consisting primarily of the cerebral hemispheres, including the neocortex, which is responsible for cognition. The remaining structure is usually only covered by a thin layer of membrane—skin, bone, meninges, and so on are all missing. Infants with this disorder, with very few exceptions, do not survive more than a few hours or possibly days after birth.

Causes:

• Folic acid may be involved in anencephaly. Folic acid supplementation in the diet of women of childbearing age has been shown in studies to significantly reduce, but not eliminate, the incidence of neural tube defects.
• In general, neural tube defects do not follow clear hereditary patterns.
• People who use certain anticonvulsants or have insulin-dependent diabetes are more likely to have a child with a neural tube defect.
• Toxins such as lead, chromium, mercury, and nickel are commonly present.

Signs and symptoms:

According to the National Institute of Neurological Disorders and Stroke (NINDS), "a baby born with anencephaly is usually blind, deaf, unaware of its surroundings, and unable to feel pain." Although some people with anencephaly are born with a main brain stem, the absence of a functioning cerebrum eliminates the possibility of them ever becoming aware of their surroundings. Breathing and responses to sound or touch are examples of reflex actions."

Diagnosis:

Anencephaly is frequently detected before birth through an ultrasound examination. Maternal serum alpha-fetoprotein (AFP) testing and detailed fetal ultrasound can be used to screen for neural tube defects such as spinal Bifida or anencephaly.