Assessment of cerebral haemodynamics and vascular reserve in patients with symptomatic carotid artery occlusion: an integrated MR method.

We describe an MR-based methodology designed to study cerebral haemodynamic compromise in patients with symptomatic carotid occlusions. We present the results of eight patients who underwent MR angiography of the cervical carotids and circle of Willis, MR imaging of the brain and dynamic gadolinium MR perfusion studies before and after the injection of the carbonic anhydrase inhibitor acetazolamide. All patients showed increased transit times in the symptomatic hemisphere at rest indicating reduced flow. The transit time asymmetries became more pronounced after acetazolamide in all patients because of failed vasodilatation on the affected side. There was an inverse correlation between the degree of increased transit time and the degree of collateralisation around the circle of Willis. We believe that demonstration of both macroscopic vascular anatomy and microvascular reserve is important when assessing patients with possible low-flow states and the described method is a robust means of obtaining that data.