Compensation Of Circle Of Willis And Its Relationship With Cerebral Infarcts In Patients With Unilateral Carotid Artery Stenosis-A MR Study

Part 1: A study of Circle of Willis completness and variation on MRA in patients with unilateral internal carotid artery stenosisPurpose: To assess the completeness and variation of the circle of Willis in patients with unilateral internal carotid artery (ICA) stenosis of different degree and to compare this with control group without internal carotid artery stenosis.Methods: MRA was performed in 77 mild-moderate ICA stenosis patients, 62 severe ICA stenosis- occlusion patients and 92 control subjects. Patients were classified according to the severity of ICA stenosis by US decision : patients with unilateral ICA stenosis <70%(group mild-moderate, n=77), patients with unilateral stenosis 70% to 100% (group severe- occlusion , n=62) and patients without ICA stenosis (group control, n=92). 3D TOF MRA was performed in all the patients to observe the presence of completeness and variance , and to assess the types of circle of Willis and completness of anterior and posterior collateral pathways in the circle of Willis.Results: In the patients we found difference of type constitution and completeness between patient group and controls. The completeness percentage of anterior part of circle of Willis decreased with the degree of ICA stenosis and the completeness percentage of posterior part of circle of Willis with degree of stenosis has no significant change. Part 2: A study of Circle of Willis artery presentation and diameters on MRA in patients with unilateral internal carotid artery stenosisPurpose: To assess the presence and diameters of anterior and posterior collateral pathways in the circle of Willis in patients with unilateral carotid artery (ICA) stenosis of different degrees and to compare this with control group without carotid artery stenosis.Methods: 3D TOF MRA was performed in 77 mild-moderate ICA stenosis patients, 62 severe ICA stenosis- occlusion patients and 92 control subjects. Patients were classified according to severity of ICA stenosis by US decision : patients with a unilateral ICA stenosis <70%(group mild-moderate, n=77), patients with a unilateral stenosis≥70% to 100% (group severe- occlusion , n=62) and patients with no ICA stenosis (group control, n=92). TOF MRA was performed in all the patients to evaluated the presence and diameter of the anterior communicating artery (ACoA), the A1 segments of the anterior cerebral arteries, and the posterior communicating arteries (PCoA, ipsilateral and contralateral) and the P1 segments of the posterior cerebral arteries(ipsilateral and contralateral). Diameters Comparison between patients and controls was made by using the Analysis of Variance. Presence percentage comparison between patients and controls was made using the X2 test.Results: In the patients we found morphology adaptation of circle of Willis. A high presence percentage and larger Mean diameters was found in ACoA, contralateral A1, ipsilateral PCoA and ipsilateral P1; The adaptation was more obvious in severe-occlusion group. More invisible ipsilateral A1 segments and a smaller Mean diameter of ipsilateral A1 segments were found, which has a relationship with degree of stenosis.Conclusion: A morphology and diameter adaptation of circle of Willis exists in ICA stenosis patients, and occurs more obviously in patients with severe ICA stenosis-occlusion compared with mild-moderate group and controls, which suggests a relation between degree of ICA stenosis and morphology and diameter of circle of Willis. Part 3: A MRI Study of Relationship Between Circle of Willis and the Incidence and Location of Infarcts in patients with unilateral internal carotid arteriy stenosisPurpose: The purpose of the present study was to assess whether the presence of infarcts is related to the collateral ability of the circle of Willis in patients with unilateral carotid artery (ICA) stenosis of different degree.Methods: 3D TOF MRA and MRI was performed in 39 mild-moderate ICA stenosis patients, 50 severe ICA stenosis-occlusion patients. The patients were classified according to severity of ICA stenosis by US decision : patients with a unilateral ICA stenosis <70%(group mild-moderate, n=77), patients with a unilateral stenosis≥70% to 100% (group severe-occlusion, n=62). 3D TOF MRA was performed in the patients to evaluated the present percentage of the component vessels in the circle of Willis, including the anterior communicating artery (ACoA), the A1 segments of the anterior cerebral arteries, and the posterior communicating arteries (PCoA, ipsilateral and contralateral) and the P1 segments of the posterior cerebral arteries(ipsilateral and contralateral). MRI was performed in patients to evaluate the incidence and location of cerebral infarcts. The present percentage of the collateral arteries of circle of Willis with different infarcts location was compared.Results: The patients with mild-moderate ICA stenosis have a decreased incidence of infarct compared with group severe-occlusion. The ACoA has more important value in protection of infarcts than other collateral arteries. The perforating arteries infarct has more incidence than other types of infarct in both groups, and have a relationship with the present percentage of ACoA and ipsilateral PCoA .Conclusion: The completeness of circle of Willis has a protective value in patients with unilateral ICA stenosis.The ACoA and ipsilateral PCoA play the most important role in circle of Willis.