• CNS development (week 3)
    •  neuroectoderm (a subtype of ectoderm) → neural plate → brain and spinal cord 
  • Neural tube gives rise to
    • forebrain (prosencephalon) 
      • telencephalon 
        • cerebral cortex, lateral ventricles, caudate, putamen, hippocampus, olfactory bulbs
      • diencephalon
        • thalami, mammillary bodies, neurohypophysis, pineal gland, retina, optic nerve, chiasm, and tract
    • midbrain (mesencephalon)
    • hindbrain (rhombencephalon)
      • metencephalon
        • pons, cerebellum
      • mylencephalon
        • medulla
Neural tube defects
  • Failure of neuropores to fuse during week 4
    • vertebral arches do not fuse resulting in a connection between amnionic cavity and spinal canal
    • defect tends to occur in lumbosacral region
    • can be detected by testing maternal blood for ↑ α-fetoprotein (AFP)
      • if elevated and neural tube defect is present, then amniocentesis will show ↑ α-fetoprotein (AFP) and ↑ acetylcholinesterase 
    • associated with maternal folate deficiency commonly caused by: 
      • low folic acid intake during pregnancy 
      • medications that interfere with folate utilization 
        • Valproate, methotrexate, sulfasalazine, phenytoin
  • Spina bifida oculta
    • least severe variation with dura intact and no herniation
    • tuft of hair in lumbosacral region 
  • Spina bifida with meningocele
    • only meninges herniate through spinal defect forming a CSF filled sac, but spinal cord remains in spinal canal
  • Spina bifida with meningomyelocele
    • meninges and spinal cord herniate through defect

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