Which among the following is a neural tube defect
**Core Concept**
The neural tube defect is a congenital anomaly resulting from the incomplete closure of the neural tube during embryonic development. This occurs between the 23rd and 26th days of gestation, leading to various physical and neurological abnormalities.
**Why the Correct Answer is Right**
The correct answer is a neural tube defect, specifically anencephaly. Anencephaly is a condition where a significant portion of the brain, skull, and scalp are absent due to the failure of the anterior neuropore to close. This defect occurs when the neural folds fail to properly fuse, resulting in the absence of a major portion of the brain and skull.
**Why Each Wrong Option is Incorrect**
**Option A:** Menkes disease is a disorder affecting copper metabolism, leading to copper deficiency and resulting in hair abnormalities, growth retardation, and neurodevelopmental delays. It is not a neural tube defect.
**Option B:** Spina bifida is a neural tube defect, but it is characterized by the incomplete closure of the posterior neuropore, leading to a defect in the spine and potentially affecting the spinal cord.
**Option C:** Down syndrome is a genetic disorder caused by an extra copy of chromosome 21, leading to intellectual disability, distinct facial features, and various physical abnormalities. It is not a neural tube defect.
**Clinical Pearl / High-Yield Fact**
Neural tube defects are often associated with a family history of similar conditions, and women with a prior history of a neural tube defect are at increased risk of recurrence. Folic acid supplementation before and during pregnancy can significantly reduce the risk of neural tube defects.
**Correct Answer:** B. Spina bifida