Which condition is described as the most common neural tube defect in this material?

• A. Anencephaly
• B. Spina Bifida Occulta
• C. Encephalocele
• D. Caudal Regression

Answer: (A)

Neural tube defects happen when the neural tube fails to close properly very early in development. Among cranial neural tube defects discussed in this material, anencephaly is described as the most common. This condition results from failure of the cranial end of the neural tube to close, so the calvarium and much of the forebrain do not form. On ultrasound, it stands out because the skull cap is absent and brain tissue is not developed above the orbits, making the finding quite apparent early in gestation. It’s frequently highlighted in teaching materials because it is readily identifiable and, unfortunately, incompatible with life, which helps explain its prominence in prenatal imaging discussions. In contrast, spina bifida occulta tends to be occult and less apparent on prenatal scans, encephalocele is less common and involves a skull defect with herniation of brain tissue, and caudal regression is a rarer malformation.