EXPERIMENTAL INTRACEREBRAL HEMORRHAGE IN RATS - MAGNETIC-RESONANCE-IMAGING AND HISTOPATHOLOGICAL CORRELATES

Background and Purpose Intracerebral hemorrhage is associated with a c onsiderable proportion of strokes and head injuries. The mechanism of brain cell injury associated with hemorrhage may be different from tha t due to pure ischemia. Therefore, it is essential that models of intr acerebral hemorrhage be developed and well characterized. The purpose of this study was to obtain high-field MR images of rat brain at progr essive times after induction of intracerebral hemorrhage and to correl ate the images with behavior and histological evolution.Methods Intrac erebral hemorrhage was induced in rats by injection of bacterial colla genase and heparin into the caudate nucleus. Histopathological changes and corresponding MR images were studied from 30 minutes to 3 weeks a fter injection. Behavioral changes were also followed for 3 weeks. Res ults Histological correlation showed that MR is capable of resolving t he accumulation and degeneration of the hematoma, a centripetal wave o f neutrophils infiltrating from the surrounding tissue beginning at 12 hours, and centripetal invasion of macrophages beginning at 48 hours. Widespread white matter edema was clearly evident on MR images for 1 week after the hemorrhage. Medium-sized striatal neurons were lost in the tissue surrounding the hematoma. Behavioral improvement was rapid during resolution of the edema but incomplete at 3 weeks. Conclusions MR images correlate very well with histological changes in this experi mental model of intracerebral hemorrhage and can therefore be used to follow changes due to drug treatments in vivo. The intense neutrophili c response to this lesion may contribute to neuronal injury at the per iphery of the hematoma.