All of the following are neural tube defects except:
**Core Concept**
Neural tube defects (NTDs) are congenital anomalies that arise from the incomplete closure of the neural tube during embryonic development. This results in defects in the brain and spinal cord, leading to various clinical manifestations.
**Why the Correct Answer is Right**
The correct answer is D. The neural tube defects listed in options A, B, and C are all well-documented conditions that involve the brain and spinal cord. **Anencephaly**, **Spina Bifida**, and **Meningocele** are all characterized by the failure of the neural tube to close properly, leading to a range of clinical symptoms. In contrast, the correct answer is a condition that does not involve the neural tube.
**Why Each Wrong Option is Incorrect**
* **Option A:** Anencephaly is a neural tube defect characterized by the absence of a significant portion of the brain and skull. It is a well-documented NTD and is therefore incorrect.
* **Option B:** Spina Bifida is a neural tube defect that involves the incomplete closure of the spinal cord and vertebral arches. It is a classic example of an NTD and is therefore incorrect.
* **Option C:** Meningocele is a neural tube defect that involves the protrusion of the meninges through a defect in the spinal column. It is a recognized NTD and is therefore incorrect.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that neural tube defects can be prevented with adequate intake of folic acid during pregnancy. The American College of Obstetricians and Gynecologists recommends a daily supplement of 400-800 mcg of folic acid for all pregnant women.
**Correct Answer:** D.