Cerebral hemodynamics in relation to patterns of collateral flow

Background and Purpose-We sought to investigate the relation between collat eral flow via different pathways and hemodynamic parameters measured by dyn amic susceptibility contrast-enhanced MRI in patients with severe carotid a rtery disease. Methods-Dynamic susceptibility contrast-enhanced MRI was performed in 66 pa tients and 33 control subjects. Patients had severe stenosis (>70%, n=12), unilateral occlusion (n=38), or bilateral occlusion (n=16) of the internal carotid artery (ICA). Cerebripetal flow and collateral flow via the circle of Willis were investigated with MR angiography, Collateral Row via the oph thalmic artery was investigated with transcranial Doppler sonography. Results-Patients with ICA stenosis had well-preserved cerebral perfusion an d were in general not dependent on collateral supply. Patients with unilate ral ICA occlusion had impaired cerebral perfusion. However, appearance time , peak time, and mean transit time in white matter were less increased in p atients with than in patients without collateral flow via the circle of Wil lis (P<0.05), Furthermore, patients with collateral flow via both anterior and posterior communicating arteries had less increased regional cerebral b lood volume than patients with collateral flow via the posterior communicat ing artery only (P<0.05). Patients with bilateral ICA occlusion had severel y compromised hemodynamic status despite recruitment of collateral supply. Conclusions-In patients with unilateral ICA occlusion, the pattern of colla teral supply has significant influence on hemodynamic status. Collateral fl ow via the anterior communicating artery is a sign of well-preserved hemody namic status, whereas no collateral flow via the circle of Willis or now vi a only the posterior communicating artery is a sign of deteriorated cerebra l perfusion.