Cerebral arterial constriction after experimental subarachnoid hemorrhage is associated with blood components within the arterial wall.

Sequential cisternal blood injections in dogs reproduce some of the morphological and physiological features seen in man after subarachnoid hemorrhage-induced vasospasm. This study reports the morphological features observed in cerebral vessels in areas exposed to subarachnoid blood. Subarachnoid hemorrhage was produced in dogs by two cisternal injections of non-heparinized autologous blood 48 hours apart. Dogs were sacrificed 48 hours after the second injection. Angiographic narrowing of the basilar artery was routinely present 48 hours after the second injection, and there was a good correlation between angiographic vasospasm and a narrowed arterial lumen at postmortem examination. All basilar arteries showed structural changes with electron microscopic examination; these included endothelial cell vacuoles, early smooth-muscle cell necrosis, intimal changes, and adventitial erythrocytes, leukocytes, and mast cells. The finding that accompanied vessel constriction most uniformly was packing of the adventitial cerebrospinal fluid spaces with erythrocytes. Angiographically visible spasm was resistant to vasodilators. These data suggest that infiltration of blood elements into the arterial wall is an important concomitant feature of morphological and angiographic vasospasm.