CNS Development

• 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