Overview 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