Anencephaly
Anencephaly (without brain) is a severe neural tube defect that occurs when the anterior-most end of the neural tube fails to close, usually during the 23rd and 26th days of pregnancy. This results in an absence of a major portion of the brain and skull. Infants born with this condition lack the main part of the forebrain and are usually blind, deaf and display major craniofacial anomalies. The lack of a functioning cerebrum will prevent the infant from even gaining consciousness. Infants are either stillborn or usually die within a few hours or days after birth. For example, anencephaly in humans can result from mutations in the NUAK2 kinase. Encephaloceles
Encephaloceles are characterized by protrusions of the brain through the skull that are sac-like and covered with membrane. They can be a groove down the middle of the upper part of the skull, between the forehead and nose, or the back of the skull. Due to the range in its location, encephaloceles are classified by the location as well as the type of defect it causes. Subtypes include occipital encephalocele, encephalocele of the carnival vault, and nasal encephaloceles (frontoethmoidal encephaloceles and basal encephaloceles), with approximately 80% of all encephaloceles occurring in the occipital area. Encephaloceles are often obvious and diagnosed immediately. Sometimes small encephaloceles in the nasal and forehead are undetected.
Maternal age has not been shown to have a huge impact on prevalence rates, but when there has been a relationship identified, older mothers along with very young mothers are at an increased risk. While maternal age may not have a huge impact, mothers that have a body mass index greater than 29 double the risk of their child having an NTD. Studies have also shown that mothers with three or more previous children show moderate risk for their next child having an NTD. References
External links
"Neural Tube Defects". MedlinePlus. U.S. National Library of Medicine. Preventing Neural Tube Birth Defects: A Prevention Model and Resource Guide: Centers for Disease Control and Prevention (CDC)