The Threshold and Neuropathology of Cerebral "Anoxic-Ischemic" Cell Change

It is essential to emphasize at the outset that anoxic-ischemic cell change is not, as the term suggests, a neuronal alteration due to anoxiaischemia alone. The term anoxia-is-chemia was introduced by Levine 1 to characterize the stress to which one cerebral hemisphere of his preparation in the rat was exposed. The whole brain endured hypoxemia because the animal was exposed intermittently to nitrogen or nitrous oxide. One cerebral hemisphere endured an additional ischemia because the common carotid artery had been ligated on that side. Within that hemisphere (and sometimes in the other) the neuronal alteration was ischemic cell change as described by Spielmeyer. 2 It is equally important to emphasize that ischemic cell change is the neuropathologic common denominator in all types of hypoxia. Thus, it is seen after (1) circulatory arrest; (2) profound hypotension without hypoxemia (oligemia); (3) hypotension with hypoxemia; (4) primary hypoxemia with secondary myocardial