Brain and Spine

Key Embryological Concepts

• Multiple processes occur during embryological development of brain and spine

• Neurulation : Ectodermal cells form midline neural plate in which folds develop then fuse to create a tube with openings at either end

  • Neurulation → neural tube + neural crest

    • –

      Neural tube → brain, spinal cord

    • –

      Neural crest → peripheral nerves, autonomic nervous system

• Neuronal proliferation : Neurons are "born" in ventricular zone; migrate peripherally to form white/gray matter

  • Glioblast cells provide metabolic/structural support to neurons; ependymal cells produce cerebrospinal fluid

• Histogenesis : Process of proliferation, migration, differentiation → development of mature cerebral cortex

  • Cerebral hemispheres formed by 11th week

  • Corpus callosum should be complete by 20 weeks

• Neuronal migration : Peak activity occurs from 11-15 weeks; majority of neurons in correct location by 24 weeks; continues up to 35 weeks

• Myelination : Occurs in orderly, predictable manner from caudal → cranial, deep → superficial, posterior → anterior

• Operculization : Development of insular cortex and infolding of sylvian fissures during weeks 11-28

• Gyral and sulcal development : Occurs in predictable fashion; continues through end of 35th week