Anencephaly
Overview
Plain-Language Overview
Anencephaly is a serious birth defect that affects the development of the baby's brain and skull. It occurs when the upper part of the neural tube, which forms the brain and skull, does not close properly during early pregnancy. This results in the absence of a major portion of the brain, skull, and scalp. The condition primarily affects the nervous system and leads to severe physical and neurological problems. Babies with anencephaly are usually born without the ability to survive long after birth. It is a type of neural tube defect and is detected before or at birth through imaging tests. The condition is not compatible with life, and affected infants typically die shortly after delivery.
Clinical Definition
Anencephaly is a congenital malformation characterized by the absence of a major portion of the brain, skull, and scalp due to failure of closure of the anterior neuropore of the neural tube during the 3rd to 4th week of embryonic development. This defect results in the absence of the forebrain and cerebral hemispheres, with preservation of the brainstem. The underlying cause is multifactorial, involving genetic and environmental factors such as folate deficiency. Clinically, it presents with absence of the cranial vault and exposed neural tissue, leading to incompatible survival beyond the neonatal period. It is a major form of neural tube defect and is associated with elevated maternal serum alpha-fetoprotein levels. The condition is diagnosed prenatally or at birth and is a critical cause of perinatal mortality.