Time-dependent variability of infarct size and hemispheric volume in experimental focal cerebral ischemia in the rabbit

Studies measuring the volume of infarcted tissue and survival after pharmacologic intervention in stroke are complicated by the potential effect of survival time on infarct volume. In this study, the volume of infarcted tissue as defined by 2,3,5-triphenyltetrazolium chloride staining was determined in rabbits at 28 h, 7 days, and 3 weeks after permanent middle cerebral artery occlusion. Compared to values at 28 h, infarcted tissue volume did not change at 7 days after occlusion, but decreased significantly by three weeks after occlusion (p < 0.01). Infarcted tissue volume expressed as a percent of hemispheric volume did not significantly change at either timepoint (p < 0.08). Immunocytochemical staining for glial fibrillary acidic protein (GFAP) indicated that infarct volume changes were not due to glial infiltration. Total hemispheric volume decreased by 7 days (p < 0.01) and 3 weeks (p < 0.01) after occlusion. These results suggest that changes in hemispheric volume may confound comparison of injury volumes in animals at differing times after occlusion. In experiments where drug treatments increase survival after focal cerebral ischemia, comparisons of the absolute infarct volume may not be valid if drug-treated animals survive greater than 1 week and untreated animals do not.