[The effect of an extracranial occlusive lesion of the branches of the aortic arch on the status of the intracranial circulation].

Unilateral occlusion of extracranial cerebral arteries results in asymmetric intracranial flow rate against unaffected regional tissue circulation. Multiple occlusions entail reduction of intracranial circulation even in satisfactory collateral circulation. Reduction of tissue cerebral circulation occurs in well-defined occlusive processes with decompensated collateral circulation in the absence of carbogenic vascular responses. Co2 reactivity may serve a criterium of collateral circulation status and a positive prognostic sign in surgery planning.