Cerebral blood flow in relation to contralateral carotid disease, an MRA and TCD study

Objective: to describe redistribution of cerebral blood flow in patients with severe internal carotid artery (ICA) stenoses in relation to contralateral ICA disease. Methods: sixty-six patients scheduled for carotid endarterectomy (CEA) were grouped according to severity of contralateral stenosis <30% [group I]; 30-69% [group II]; 70-99% [group III]; occlusion [group IV]. Transcranial Doppler (TCD) and magnetic resonance angiography (MRA) investigations were performed preoperatively. Results: TCD demonstrated a reversed flow in the contralateral anterior cerebral artery (A(1) segment) and ophthalmic artery in three-quarters of group IV patients ( p<0.001). Group IV patients also exhibited decreased blood flow velocity in the contralateral middle cerebral artery (p=0.001). MRA showed increased ipsilateral ICA and basilar artery (BA) blood flow volumes (Q-flows) in group IV patients when compared to the other groups (p<0.001). No changes in total Q-flow (ICAs + BA) were found. Conclusions: in patients considered for CEA, the severity of the contralateral ICA disease is an important determinant of the pattern of blood flow redistribution through the anterior communicating pathway and ophthalmic artery. Significant flow redistribution through the posterior communicating pathway occurs especially in patients with contralateral ICA occlusion.