Brain edema associated with progressive selective neuronal death or impending infarction in the cerebral cortex

This study examined the temporal profile of brain edema in the cerebral cortex associated with selective neuronal death or focal infarction after repeated ischemia at an intensity of ischemic insult just under and above the threshold level to induce infarction. The left carotid artery of adult gerbils was twice occluded for 10 min each time with a 5-hr interval between the blockages. In this model, focal infarction developed in coronal sections examined at the chiasmatic level (face A), whereas only selective neuronal death without infarction was found in the coronal section observed at the infundibular level (face B). In each animal, Evans blue (2%) was intravenously injected 1 hr prior to sacrifice as an indicator of blood-brain barrier (BBB) disruption. Brain edema was assessed by gravimetry in samples taken from both faces at 15 min, 5 hr, 12 hr, 24 hr, and 48 hr after the 2nd 10-min ischemia. Evans blue extravasated only in face A, corresponding to focal infarction at 24 and 48 hr after the 2nd 10-min ischemia. The specific gravities of the ischemic cortex of both faces decreased significantly from control at 15 min (P < 0.05) and had recovered by 5 hr after ischemia. By 12 hr, the specific gravities of both faces had again decreased significantly from the control values (P < 0.05), but did not differ significantly from each other. At 24 and 48 hr, the specific gravities of both faces were significantly lower than the control values (P < 0.01), and the specific gravity of face A was markedly lower than that of face B (P < 0.01). We concluded that in face B, where only selective neuronal death without infarction occurred only cytotoxic edema develops, whereas in face A, where infarction progresses, vasogenic edema develops in addition to cytotoxic edema.