Effects of subarachnoid hemorrhage from puncture of the middle cerebral artery on blood flow and vasculature of the cerebral cortex in the cat

✓ Bilateral measurements of regional cortical blood flow (CBF) and the diameter of superficial cortical arteries were made before and after puncture of the right middle cerebral arteries (MCA) of 11 cats with bilateral craniectomies. The CBF was decreased in the right cerebral hemispheres before puncture, probably because of manipulation and exposure of the MCA. Decreases of CBF occurred after MCA puncture in the contralateral cerebral hemispheres of five of seven animals without subarachnoid blood over the convexities of the hemispheres. The mean CBF value for the contralateral hemispheres was significantly lower after puncture than before. There was no consistent relationship between CBF and the calibers of surface cortical arteries. Thus, basal subarachnoid bleeding can cause decreases of CBF of the cerebral hemispheres, probably because of basal arterial spasm associated, at times, with vasomotor paralysis and failure of autoregulatory responses. If combined with increases of intracranial pressure, such decreases of CBF may be adequate to produce cerebral ischemia.