MRA flow quantification in patients with a symptomatic internal carotid artery occlusion

Background and Purpose: Flow measurements in the collateral arteries of patients with internal carotid artery (ICA) occlusions may be important to estimate the risk of future stroke. Quantitative flow measurements in cerebropetal vessels can be reliably assessed by means of magnetic resonance angiography (MRA). Methods: Fifty-four patients with transient or minor ischemic neurological deficits and an angiographically proven ICA occlusion and 16 control subjects underwent two-dimensional phase-contrast MRA quantitative flow measurements through the common carotid arteries, basilar artery, ICAs, and middle cerebral arteries (MCA). Results: Patients with a unilateral ICA occlusion and a 0% to 69% stenosis of the contralateral ICA had increased flow in the contralateral ICA (P<.005) and in the basilar artery (P<.005) compared with control subjects. Even patients with a 70% to 99% stenosis contralateral to the ICA occlusion had increased flow in the ICA (P<.05) as well as increased flow in the basilar artery (P<.001). Total cerebropetal flow was not significantly different between these patients and control subjects. Patients with bilateral ICA occlusions had an increased flow in the basilar artery (P<.001), while the total cerebropetal flow was less than in control subjects (P<.001). In all patients, flow was decreased in the ipsilateral MCA (P<.001) and in the contralateral MCA (P<.05). Conclusions: The contralateral ICA is the main supplying artery in patients with an ICA occlusion. Total cerebropetal flow decreases only when both ICAs are occluded. In patients with symptomatic ICA occlusions, an open contralateral ICA is probably important to retain the cerebral blood flow within normal limits.