Intracisternal blood injections fail to produce cerebral angiopathy in cats.

Adult cats were subjected to subarachnoid hemorrhage by three repeated intracisternal injections of autogenous nonheparinized blood (2 ml/injection) at weekly intervals. Histological studies (light and electron microscope) were made of the basilar artery and the middle cerebral arteries of all animals. In the subarachnoid-injected hemorrhaged animals, a large, organized blood clot extended uninterrupted along the lateral and ventral aspect of the medulla and pons, covering or partially encircling the basilar artery for most of its course. Smaller and less organized clots extended into various mesencephalic regions. Histologic findings in vessels from the injected hemorrhaged group were similar to those of control animals, showing neither evidence of endothelial damage, intimal proliferation, nor other significant vascular changes. The results suggest that the injection of blood into the subarachnoid space does not produce significant structural changes, but that the primary stimulus for the initiation of such pathologic events is closely tied to vessel rupture.