Evaluation Of Cerebral Perfusion And Cerebrovascular Reserve Of Patients With Unilateral Middle Cerebral Artery Stenosis

Objective：To evaluate cerebral perfusion and cerebrovascular reserve（CVR） ofpatients with unilateral middle cerebral artery(MCA）stenosis by perfusion CT (CTP)combined with CO2inhalation test.The association among the ratio of MCA stenosis,the perfusion and the CVR values was investigated.Methods:CTP were performed in31patients who were diagnosed unilateral middle cerebral stenosis before and after CO2inhalation. The basal ganglia and radialdimension were selected as interested regions(thickness,8mm). The values of cerebral blood flow (CBF)、cerebral volume(CBV）、time to peak(TTP) and mean transit time (MTT)were measured and the mean parameters values of all interested regions in each MCA territory were harvested separately.Based on the contralateral normal controls,we analyze cerebral perfusion in affected MCA territory.Then the CVR of each MCA territory was calculated according to the following formula.CVR=(CBF after CO2inhalation test-CBF before CO2inhalation test)/CBF before CO2inhalation test×100%. Patients were divided into two groups, the severe stenosis group and the moderate stenosis group. The association among the ratio of MCA stenosis,the perfusion and the CVR values was investigated.Results:①.Cerebral perfusion:In affected side of MCA territory,there were eightpatients in normal perfusion and twenty-three cases in low perfusion.②.Comparison of CBF before and after CO2inhalation test:In thirty one patients,different changes of CBF were found in affected MCA territory after CO2inhalation:CBF increased in17cases,unchanged in2cases and decreased in12cases.③.CVR:In th irty one patients,15patients had normal CVR with CVR of16patients decreased.The CVR of affected side range from-11.50%~19.50with the healthy side15.60%～21.80%.④.The correlation between the severity of stenosis in MCA andCVR:The proportion of CVR decline between the severe stenosis group and themoderate stenosis group had statistically significant,P=0.029.The degree of stenosis in MCA is correlated significantly with the changes of CVR(r=0.423,P=0.018).⑤.The correlation between the severity of stenosis in MCA and cerebral perfusion:The proportion of cerebral perfusion decline between the severe stenosis groupand the moderate stenosis group had statistically significant,P=0.032.The degreeof stenosis in MCA is also correlated significantly with the changes of cerebral perfusion(r=0.439,P=0.008).The ratio of patients with TIA between the normal cerebral perfusion group and decreased cerebral perfusion group had statistically difference(P=0.004).⑥.The correlation between cerebral perfusion and CVR:The proportion of CVR decline between the normal cerebral perfusion group and low cerebral perfusion group had statistically significant,P=0.035.The degree of stenosis inMCA is alsocorrelated significantly with the changes of cerebral perfusion(r=0.462,P=0.009).Conclusion:①.Both of the cerebral perfusion and CVR in some patients were normal.Different changes of CBF were found in affected MCA territory after CO2inhalation:CBF increased,unchanged and decreased.②.Decreased CVR is significantly correlated with the severity of stenosis in MCA..Cerebral perfusion is significantly correlated with the severity of stenosis in MCA. The changes of cerebralperfusion and CVR had a positive rank correlation. The proportion of TIA in the low cerebral perfusion group is higher that in the normal cerebral perfusion group.