Tuesday, 29 August 2017

Forebrain developmental abnormalities

Megalencephaly
  • Abnormally large brain
  • Less common than microencephaly 
Microencephaly
  • Abnormally small brain
  • Lots of causes (chromosomal abnormalities, fetal alcohol syndrome, HIV acquired in utero)
Lissencephaly
  • Decrease in number of gyri
  • Sometimes gyri are totally absent (agyria)
Polymicrogyria
  • Small, numerous, irregularly formed gyri
  • Can be caused by injury or genetic abnormality
Neuronal heterotopias
  • Neurons in inappropriate locations along migrational pathways
  • Associated with epilepsy
Holoprosencephaly
  • Incomplete separation of cerebral hemispheres across the midline
  • May have midline facial abnormalities (e.g., cyclopia, absence of olfactory cranial nerves)
Agenesis of the corpus callosum

  • Absence of white matter bundles connecting cerebral hemispheres
  • Patients may have other defects, or may be asymptomatic

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