Clinical features associated with internal carotid artery occlusion do not correlate with MRA cerebropetal flow measurements

In Vivo Assessment of the Impact of Regional Intracranial Atherosclerotic Lesions on Brain Arterial 3D Hemodynamics

BACKGROUND AND PURPOSE

Intracranial atherosclerosis induces hemodynamic disturbance, which is not well-characterized, particularly in cerebral flow redistribution. We aimed to characterize the impact of regional stenotic lesions on intracranial hemodynamics by using 4D flow MR imaging.

MATERIALS AND METHODS

4D flow MR imaging was performed in 22 symptomatic patients (mean age, 68.4 ± 14.2 years) with intracranial stenosis (ICA, n = 7; MCA, n = 9; basilar artery, n = 6) and 10 age-appropriate healthy volunteers (mean age, 60.7 ± 8.1 years). 3D blood flow patterns were visualized by using time-integrated pathlines. Blood flow and peak velocity asymmetry indices were compared between patients and healthy volunteers in 4 prespecified arteries: ICAs, MCAs, and anterior/posterior cerebral arteries.

RESULTS

3D blood flow pathlines demonstrated flow redistribution across cerebral arteries in patients with unilateral intracranial stenosis. For patients with ICA stenosis compared with healthy volunteers, significantly lower flow and peak velocities were identified in the ipsilateral ICA (P = .001 and P = .001) and MCA (P < .001 and P = .001), but higher flow, in the ipsilateral PCA (P < .001). For patients with MCA stenosis, significantly lower flow and peak velocities were observed in the ipsilateral ICA (P = .009 and P = .045) and MCA (P < .001 and P = .005), but significantly higher flow was found in the ipsilateral posterior cerebral artery (P = .014) and anterior cerebral artery (P = .006). The asymmetry indices were not significantly different between patients with basilar artery stenosis and the healthy volunteers.

CONCLUSIONS

Regional intracranial atherosclerotic lesions not only alter distal arterial flow but also significantly affect ipsilateral collateral arterial hemodynamics.

Redistribution of cerebropetal blood flow in patients with carotid artery stenosis measured non-invasively with fast cine phase contrast MR angiography

The purpose was to evaluate the blood flow redistribution in the neck vessels of patients with internal carotid artery (ICA) stenosis. Eighty-six patients with ICA stenosis underwent contrast-enhanced magnetic resonance angiography (CEMRA) and fast 2D phase contrast (2D-PC) sequence to measure the mean blood flow (MBF) of ICA, basilar artery (BA) and middle cerebral artery (MCA). CEMRA revealed 53 severe stenoses, 45 moderate stenoses and 3 occluded vessels. Patients with a unilateral severe ICA stenosis had a significantly reduced MBF of the ICA compared to the control group; the MBF reduction of the severely stenosed ICA was less conspicuous if associated with a controlateral severe stenosis. The MBF of the BA increased significantly in the presence of the bilateral severe ICA stenosis and in the ICA occlusion. The MBF of the MCA was unchanged in the presence of various degrees of ICA stenosis. Measurement of MBF with fast PC MRA permits cerebropethal blood flow assessment and gives additional information in grading ICA stenosis. The reduced MBF of a severe ICA stenosis has to be considered with caution since it depends also on the status of the controlateral ICA and may be considered a confident parameter only in case of unilateral carotid stenosis.