Question:
Which of the following is the earliest to be diagnosed by ultrasonography (USG)?
Which of the following is the earliest to be diagnosed by ultrasonography (USG)?
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The defect with the most obvious gross cranial abnormality is seen soonest.
Updated On: Jun 24, 2026
- Anencephaly
- Prosencephaly
- Meningocele
- Spina bifida
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The Correct Option is A
Solution and Explanation
Step 1: Frame the question.
The question asks which neural tube/cranial anomaly is recognised earliest on antenatal ultrasound.
Step 2: Recall anencephaly.
Anencephaly is absence of the cranial vault and cerebral hemispheres (acrania with absent forebrain). The missing calvarium produces a strikingly abnormal cranial silhouette that is readily seen on ultrasound. The absence of normal cranial ossification and brain can be appreciated from the late first trimester to early second trimester, earlier than the other listed defects.
Step 3: Compare the others.
Holoprosencephaly (prosencephalic defect), a meningocele and spina bifida involve more subtle structural findings that generally become reliably detectable somewhat later, requiring careful imaging of the spine or midline brain structures. Their characteristic signs are typically confirmed later than the gross cranial absence of anencephaly.
Step 4: Conclusion.
Anencephaly is the earliest of these to be diagnosed by USG.
Correct answer: Anencephaly.
The question asks which neural tube/cranial anomaly is recognised earliest on antenatal ultrasound.
Step 2: Recall anencephaly.
Anencephaly is absence of the cranial vault and cerebral hemispheres (acrania with absent forebrain). The missing calvarium produces a strikingly abnormal cranial silhouette that is readily seen on ultrasound. The absence of normal cranial ossification and brain can be appreciated from the late first trimester to early second trimester, earlier than the other listed defects.
Step 3: Compare the others.
Holoprosencephaly (prosencephalic defect), a meningocele and spina bifida involve more subtle structural findings that generally become reliably detectable somewhat later, requiring careful imaging of the spine or midline brain structures. Their characteristic signs are typically confirmed later than the gross cranial absence of anencephaly.
Step 4: Conclusion.
Anencephaly is the earliest of these to be diagnosed by USG.
Correct answer: Anencephaly.
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