The effects of acute proximal basilar artery occlusion on the primate cerebral circulation

The effects of acute proximal basilar artery occlusion on blood flow, autoregulation and CO2 reactivity in four separate regions of the brain (cerebral cortex, thalamus, brainstem and caudal pons) were studied and compared in 30 anaesthetised baboons. Significant flow changes were seen in all areas of the basilar territory, even in instances where the posterior communicating artery was observed to be relatively large. Flow changes were also seen in regions of the brain remote from the basilar territory. Areas furthest from the collateral blood supply showed the largest changes in blood flow, as has previously been shown in the case of proximal middle cerebral artery occlusion. From this, one can predict that in surgery, the more rostral the occlusion of the artery, the safer the procedure should be. At normal blood pressure, while the collateral circulation to the brainstem and thalamus was adequate to maintain normal electrical function after basilar occlusion, the flow was totally inadequate to maintain autoregulation or CO2 reactivity in the basilar territory.