- Causes:
- Atherosclerosis 40-60%
- Embolism 15-40%
- Intracerebral hemorrhage 10-15%
- Subarachnoid hemorrhage 10-15%
- Others 5-20%
- Brain has an absolute requirement for oxygen; following cessation of blood flow:
- 11 sec Unconscious
- 40 sec EEG flat
- 3 min Glucose gone; irreversible
- 5-7 min Tissue ATP gone
- Different cell types show different sensitivities to ischemia; in order: neurons, oligodendrocytes, astrocytes, microglial cells, vessels
- Different regions of the brain show different sensitivities to global ischemia; in order: hippocampus (Sommer sector [CA-I], CA-II spared), external pyramidal layer (layer 3) of the neocortex, Purkinje cells of the cerebellum, inferior olivary neurons, subthalamic nucleus
- Histologic evidence of neuronal anoxic/ischemic injury: acidophilic degeneration, glassy cytoplasm, loss of NissI substance, hyperchromatic nuclei, shrinkage of neuron with increase in perineuronal space