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Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development. In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo begin to change shape and form the neural tube.
These defects are caused by failure of the neural tube to close completely during fetal development. Encephaloceles cause a groove down the middle of the skull, or between the forehead and nose, or on the back side of the skull. The severity of encephalocele varies, depending on its location. [1]
Failure of neurulation, especially failure of closure of the neural tube are among the most common and disabling birth defects in humans, occurring in roughly 1 in every 500 live births. [42] Failure of the rostral end of the neural tube to close results in anencephaly, or lack of brain development, and is most often fatal. [43]
Women who have already had a baby with spina bifida or other type of neural tube defect, or are taking anticonvulsant medication, should take a higher dose of 4–5 mg/day. [69] However, the daily requirement of folate and the recommended folate blood levels to prevent neural tube defects are not well established. [59]
Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. [1] It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fails to close, usually between the 23rd and 26th day following conception. [2]
For a short time, the neural tube is open both cranially and caudally. These openings, called neuropores, close during the fourth week in humans. Improper closure of the neuropores can result in neural tube defects such as anencephaly or spina bifida. The dorsal part of the neural tube contains the alar plate, which is associated primarily with ...
Narrowing can be a defect from birth that results in congenital aqueductal stenosis. Developmental errors that could result in this defect include abnormal folding of the neural plate which causes the neural tube to be narrowed from birth. [3]
The defect can be located anywhere from the cervical region to the sacrum, or through the entire length of the spine. Typical defects are clefts or splits that open the spine to the exterior environment. Rachischisis occurs around 3–4 weeks after conception when the posterior neuropore of the neural tube does not close completely. It is a ...