Anencephalus

Anencephalus, also known as anencephaly, is a serious congenital disorder characterized by the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. This condition is a type of neural tube defect (NTD) that results from the failure of the neural tube to close properly during the first few weeks of pregnancy.

Anencephaly-web

Anencefalia

Pathophysiology

Anencephalus occurs when the cephalic (head) end of the neural tube fails to close, usually between the 23rd and 26th day of gestation. This results in the absence of a large portion of the brain, including the cerebrum, which is responsible for cognitive function, sensory processing, and voluntary movement. The brainstem, which controls basic life functions such as breathing and heartbeat, may be present but is often malformed.

Causes

The exact cause of anencephalus is not fully understood, but it is believed to result from a combination of genetic and environmental factors.

Genetic Factors

Certain genetic mutations and chromosomal abnormalities have been associated with an increased risk of anencephalus. However, no single gene has been identified as the cause.

Environmental Factors

Environmental factors, such as maternal nutrition and exposure to certain teratogens, can also play a role. A deficiency in folic acid during early pregnancy is a well-known risk factor for neural tube defects, including anencephalus.

Diagnosis

Anencephalus can often be diagnosed before birth through prenatal screening.

Ultrasound

A prenatal ultrasound can detect anencephalus as early as the first trimester. The absence of the cranial vault and brain tissue is usually apparent.

Amniocentesis

Amniocentesis may be performed to analyze amniotic fluid for elevated levels of alpha-fetoprotein (AFP), which can indicate a neural tube defect.

Prevention

The risk of anencephalus can be reduced by ensuring adequate intake of folic acid before conception and during early pregnancy. It is recommended that women of childbearing age take a daily supplement of 400 micrograms of folic acid.

Prognosis

The prognosis for infants with anencephalus is extremely poor. Most affected infants are stillborn or die shortly after birth. There is no cure or standard treatment for anencephalus, and management is focused on providing supportive care.

Epidemiology

Anencephalus occurs in approximately 1 in 1,000 pregnancies, but many of these pregnancies result in miscarriage. The condition is more common in females than in males.

See also

• Neural tube defect
• Spina bifida
• Folic acid