Encephalocele anencephaly
Overview
Anencephaly is a cephalic disorder that results from a neural tube defect that occurs when the cephalic (head) end of the neural tube fails to close, usually between the 23rd and 26th day of pregnancy resulting in the absence of a major portion of the brain, skull, and scalp. Children with this disorder are born without a forebrain, the largest part of the brain consisting mainly of the cerebral hemispheres (which include the isocortex, which is responsible for higher level cognition, i.e., thinking). The remaining brain tissue is often exposed—not covered by bone or skin.
Causes
The cause of anencephaly is disputed. From a developmental point of view, there is a direct association between an impairment of the fetus's swallowing mechanism and the occurrence of anencephaly, but the reason for impairment is not exactly known. Genetically, neural tube defects do not follow direct patterns of heredity, though there is some indirect evidence of inheritance, and recent animal models indicating a possible association with deficiencies of the transcription factor TEAD2. Studies show that a woman who has had one child with a neural tube defect such as anencephaly, has about a 3% risk to have another child with a neural tube defect.
Diagnosis
Anencephaly can often be diagnosed before birth through an ultrasound examination. The maternal serum alpha-fetoprotein (AFP screening) and detailed fetal ultrasound can be useful for screening for neural tube defects such as spina bifida or anencephaly.
Prognosis
There is no cure or standard treatment for anencephaly and the prognosis for affected individuals is poor. Most anencephalic babies do not survive birth, accounting for 55% of non-aborted cases. If the infant is not stillborn, then he or she will usually die within a few hours or days after birth from cardiorespiratory arrest