The medical term for a baby born without major parts of the brain and skull is Anencephaly. This is a severe congenital defect affecting the central nervous system, occurring very early in embryonic development. Anencephaly is classified as a type of neural tube defect (birth defects of the brain and spine). The condition involves the failure of the upper part of the neural tube to close completely, resulting in the absence of the forebrain, cerebrum, and the bones that cover the head. This profound lack of structures means the condition is universally fatal.
Anencephaly: The Medical Condition
Anencephaly is characterized by the absence of the cerebrum, the largest part of the brain responsible for thinking, vision, hearing, and movement. The defect also results in the malformation or absence of the cranial vault, meaning the skull bones that protect the brain are missing or incomplete. The remaining neural tissue is often exposed, lacking a covering of skin or bone.
While the forebrain and cerebrum are absent, the brainstem is often present in a rudimentary form. The brainstem is responsible for automatic, life-sustaining functions such as breathing and basic reflexes. However, the lack of a functioning cerebrum means the infant is permanently unconscious and unable to perceive pain or develop awareness.
The condition is identified by the specific ICD-10 code Q00.0. Due to the severity of the neurological malformation, anencephaly is incompatible with prolonged life. Most affected pregnancies end in miscarriage, stillbirth, or the infant dies shortly after birth, usually within a few hours or days.
Neural Tube Development and Etiology
Anencephaly arises from a disruption in neurulation, the process where the neural tube forms in the developing embryo. The neural tube is a flat plate of tissue that folds and closes to form the brain and spinal cord. This closure process begins around 18 days after conception and is completed quickly.
Anencephaly occurs when the cephalic (head) end of the neural tube fails to close between the 23rd and 26th day following conception. This failure exposes the developing brain tissue to amniotic fluid, causing the tissue to degenerate. This error often happens before a person is aware they are pregnant.
The exact cause is believed to be a multifactorial combination of genetic and environmental factors. Risk factors include maternal conditions such as uncontrolled pre-existing diabetes and maternal obesity. Exposure to certain anti-seizure medications during early pregnancy can also increase the risk.
Prenatal Detection and Clinical Outcome
Anencephaly can often be detected before birth through routine prenatal screening. One initial method involves measuring maternal serum alpha-fetoprotein (MSAFP) levels, a protein produced by the fetus found in the mother’s blood. An elevated level of AFP can suggest an open neural tube defect like anencephaly.
The diagnosis is typically confirmed using a high-resolution ultrasound, which clearly shows the absence of the cranial vault and forebrain. Ultrasound can reliably identify the condition as early as the first trimester. This certainty allows healthcare providers to offer counseling and discuss the prognosis with the parents.
The clinical outcome is uniformly poor, as there is no cure or effective treatment. Care focuses entirely on supportive measures and providing comfort for the infant. Infants born alive lack the necessary brain structures to survive long-term, and death is expected shortly after delivery.
Reducing the Risk of Neural Tube Defects
Public health efforts focus on preventative steps, primarily through ensuring adequate nutrient intake. The most effective strategy for reducing the risk of anencephaly and other neural tube defects (NTDs) is the consumption of folic acid, a synthetic form of the B vitamin folate (Vitamin B9). Folic acid supplementation can reduce the risk of NTDs by 50% or more.
Since the neural tube closes early, it is recommended that all individuals capable of becoming pregnant consume 400 micrograms (0.4 mg) of folic acid daily. This intake should begin at least one month before conception and continue through the first three months of pregnancy.
Individuals who have previously had an NTD-affected pregnancy should consult a healthcare provider, as they may be recommended a higher daily dose, often 4,000 micrograms.
Managing pre-existing health conditions is another important step in prevention. Women with diabetes can significantly reduce their risk by achieving strict control of their blood glucose levels before and during early gestation. Maintaining a healthy body weight also contributes to lowering the overall risk of NTDs.