<s>[INST] context: Neural tube defect

Neural tube defects account for most congenital anamalies of the CNS.
It results from failure of neural tube to close spontaneously between the 3rd and 4th week of in utero development.
Lumbo-sacrol region is the most common site Etiology
NTDs have multiple etiological factors -


Maternal diabetes                                                                                                   
Zinc and folate deficiency
Maternal exposure to alcohol, radiation, valproate, carbamazepine
Trisomy 13 and 15


Maternal malnutrition is an important risk factor for development of NTD. There is decreased maternal folate levels in NTD affected pregnancies --> Periconceptional folic acid supplementation decreases the occurrence of NTD

Pathogenesis

The human nervous system develops from neuroectoderm.
During development, behind neuroectoderm lies the mesoderm that encloses the notochord which is derived from endoderm.
Vertebral bodies develop from the mesoderm around the notochord.
Neuroectoderm forms invagination ---> Neural groove.
This neural groove separates from overlying surface ectoderm and becomes neural tube.
From developing vertebral bodies, two dorsal projection extends, which grow around the neural tube and form vertebral arch (pedicle and lamina).
Failure of these vertebral arches to fuse give rise to Neural tube defect. [/INST] question: Neural tube defects are prevented by – | options: A: Pyridoxin B: Folic acid C: Thiamine D: Iron | answer: B </s>