Diffuse cerebral ischemia in the cat: III. Neuropathological sequelae of severe ischemia.

The neuropathological consequences of sever diffuse cerebral ischemia were investigated in an animal model in which postischemic alterations of regional brain blood flow and energy metabolism had been previously characterized. Pentobarbital-anesthetized cats received either 15 or 30 minutes of ischemia produced by basilar artery and bilateral carotid artery occlusions plus mild hypotension; this was followed by 60 to 90 minutes of normotensive recirculation. The brains were perfusion-fixed for light microscopy. Both insult durations resulted in unequivocal ischemic cell change affecting neurons of the cerebral neocortex, striatum, thalamus, and hippocampus and portions of the rostral brainstem. Animals with 30 minutes of prior ischemia differed from those with 15 minutes of ischemia in showing a more apparent regional accentuation of ischemic change in the parasagittal cortical gyri--the sites of previously documented focal postischemic heterogeneities of blood flow and metabolism. In other respects, however, the overall distribution and spectrum of severity of the ischemic alterations were similar for the two insult durations. These data support the view that significant permanent neuronal injury may result from a period of cerebral ischemia as brief as 15 minutes.