The nervous system of higher animals is exceedingly sensitive to anemia or other physiologic conditions which involve a local lack of oxygen. Muscle tissue which has been supplied inadequately with this essential element or perhaps completely deprived of it for not inconsiderable periods of time may still show a satisfactory recovery of contractile power when the circulation is suitably restored and the resuscitating oxygen reaches the asphyxiated tissue-cells, but this is not the case with the nervous tissues. The nerve-cells of different classes and positions show differences in sensitiveness to anemia. Those of the cerebrum and cerebellum are unquestionably most readily damaged by oxygen starvation. There is evidence to show, for example, that eight minutes of complete anemia may permanently eliminate the function of some of the cells of the cortical areas. If the blood-supply there is wanting for more than twenty minutes it is rarely possible to discover restoration when the circulation is reestablished. In descending to the lower levels of the cerebrospinal nervous system the resistance to the detrimental effects of anemia or the immunity from permanent damage by lack of oxygen increases appreciably. In sequence the cells of the spinal bulb, the spinal cord and the spinal ganglia, respectively, appear to withstand anemia for longer and longer periods, so that a cessation of the circulation for eight or ten minutes may be of minor significance and permit of prompt complete recovery when the blood-supply is restored. Anemia of the spinal cord for an hour, however, is reported to be sufficient to cause necrosis of all the nervous elements.
The Resistance of Various Nerve-Cells to Anemia. JAMA. 2013;310(23):2570. doi:10.1001/jama.2013.5471