Anencephaly is a congenital birth defect and a type of neural tube defect.
Anencephaly or “open skull” is a congenital anomaly of the neonates in which part of or whole of the head, brain or skull are absent. The children with anencephaly show gross facial and cephalic deformities. As a relatively prevalent disorder, anencephaly is one of the common causes of still births and neonatal deaths in high risk populations.
Neural tube defects are implicated in the genesis of anencephaly and are caused by the following:
The condition is closely related to spina bifida, another of the neural tube defects in which spine fails to develop.
Anencephaly is a sporadic disorder, with unequal geographical distribution. The prevalence of this condition is 1:10,000. The exact prevalence of anencephaly is unknown due to high incidence of miscarriages. The risk of anencephaly is higher in children born to women who have given birth to anencephalic children before. Female newborns are affected more as compared to males. Hispanics have a higher incidence of the disease as compared to Native Africans.
The reason for anencephaly for being relatively prevalent is that most of the neural tube defects arise during the 3rd and 4th week of pregnancy, the time when women are still unaware of pregnancy.
There is a slight familial tendency to anencephaly and it may run in families with a history of congenital birth defects. The pattern of inheritance is however, still unclear.
Most of the organs develop during the 3rd and 4th week of pregnancy. Neural tube is the structure that gives rise to the central nervous tissues, brain and spinal cord in fetuses. Normally, neural tube starts as a sheet of cells that soon come together to form a tube and ultimately closes at 24th to 26th day. When the cephalic or the “head end” of the neural tube fails to close properly, the brain tissues are exposed to the surrounding amniotic fluid, the pressure of which causes regression of the tissues. As a result, brain tissues fail to develop. These cases are usually born with exposed head tissues. The remaining brain tissue is often not covered by meninges, skin or bone.
Although central brain stem might be present, the most of the forebrain, the cerebrum and cerebellum are absent in such babies. Although the breathing reflex is present in such babies, they never gain consciousness due to the absence of cerebrum.
Anencephaly is rarely compatible with life. 75 % of the cases are still born. The remaining 25 % of the neonates die within an hour or at the latest, a week after birth. Ideally, anomaly scans should be performed prenatally and if anencephaly is detected, the pregnancy should be terminated.
Anencephalic becomes apparent at birth. The neonates usually present with absence of the skull with exposed rudimentary brain tissue. There is also craniofacial disfiguration. The ears may be folded and cleft palate may also be present. There are a number of other defects including congenital heart defects.
No current therapy is available for correction of this defect in-vitro or even after birth. Abortion upon early diagnosis of congenital anomalies on ultrasound is still debated upon due to ethical issues.
Supportive therapy is given to the neonates to keep them warm and to prevent the contact of exposed tissues with hazardous substances. The parents are also counselled and the mother is advised to take folic acid supplementation in the next pregnancy in order to prevent anencephaly and other neural tube defects.
Anencephaly is partial or complete absence of brain and head. The children born with anencephaly are severely disfigured, having exposed internal head structures. Blindness and deafness is common in these children. The problem arises due to the deficiency of a vitamin, folic acid, in diet. Such babies usually die soon after they are born. Intake of folic acid during pregnancy can reduce the risk of this disorder.