Failure of closure of the neural tube at the caudal neuropore (day 26–28) results in which of the following?
- A Myelomeningocele (spina bifida) ✓
- B Anencephaly
- C Holoprosencephaly
- D Dandy-Walker malformation
Correct answer: A. Myelomeningocele (spina bifida)
Explanation
The neural tube closes in a zipper-like fashion between days 22–28. Failure of the caudal neuropore (which closes around day 26–28) results in defects of the lower spinal cord — spina bifida (myelomeningocele). Failure of the rostral neuropore (which closes around day 24–26) results in anencephaly (failure of brain formation). Holoprosencephaly results from failure of prosencephalon division (related to SHH and other gene mutations). Dandy-Walker malformation results from failure of development of the posterior fossa.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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