Evaluation Of Cerebrovascular Reserve In Patients With Unilateral Middle Cerebral Artery Stenosis

Objective：To evaluate the cerebrovascular reserve（CVR） with Single-Photon EmissionComputed Tomography （SPECT） and CO₂inhalation text in patients with unilateralmiddle cerebral artery stenosis.Methods: SPECT were performed in24patients twice who were diagnosed unilateralmiddle cerebral stenosis with Digital subtraction angiography.The first SPECTexamination,the subjects lied10min in a quiet, dimly room to avoid the sound and lightstimulation,each study was acquired60min after intravenous injection of about99mTc-ECD925MBq（25mCi）.Drew the outline of12Regions of Interest（ROI） withcomputer,6in right and6in left.The next day perfromed the second SPECT examinaionwith the CO₂inhalation text, connected to a breathing mask and a gas conduit, thenclosed buckle on the subject ’s face, adjusted the gas flow rate in4L/min, breathed in1min5%CO₂and95%O₂with mouth, and the SPECT study was performed by thesame procedure with the first. The regional cerebral blood flow （rCBF%）of all ROIwere calculated,compared the normal side and the stenosis side,before and after CO₂inhalation test, then analyzed the date with Semi-quantitative analysis.Results:①.There were29patients meeting the standards,2patients transferred to theDepartment of Cardiology for coronary heart disease,2patients rejected the SPECTstudies after DSA,1patient perfromed adverse events after after intravenous injectionof99mTc-ECD.Then there were24patients,20males, and4females, mean age is（53.79±14.58） years old,13patients were the left middle cerebral artery （MCA）stenosis,11patients were the right MCA stenosis,14patients have small infactions inthe side of lesion,10patients transient ischemic attack（TIA） in the side of lesion, meanMCA stenosis ratio of the24patients was （82.25±2.38）%, all patients have collateral circulation, the main collateral circulation was anterior cerebral artery （ACA） whichwere contirmed with digital subraction angiography（DSA）, only3patients haveposterior cerebral artery （PCA） for collateral circulation.②.According to the results of ROI semi-quantitative analysis,the cerebral blood flowreaction to CO₂were divided into4types. A type, there were no difference of rCBF%inresting and after CO₂inhalation text in121ROI; B type, rCBF%of119ROI werenormal in resting, and decreased after CO₂inhalation text; C type, rCBF%weredecreased in resting, and more decreased after CO₂inhalation text in12ROI;D type,rCBF%of38ROI were decreased in resting, after CO₂inhalation text there wereincreased.③.InAtype,there were no difference of rCBF%in resting and after CO₂inhalation textin121ROI.There were2patients who rCBF%were normal in12ROI before and afterCO₂inhalation.④.And in B、C type, rCBF%were decreased in132ROI after CO₂inhalation text,mean CVR decreased, and2、11ROI had the most decreased number,each was15.2%、16.7%.Conclusion:①.There were normal CVR in patients with unilateral middle cerebralartery stenosis;②.there were four different types conditions for CO₂inhalation text incerebral,B and C types meand CVR decreased;③.the CVR of posterior watershedprobably decreased much more in patients with unilateral middle cerebral arterystenosis whose CVR were decreased,maybe associated with tissue perfusion ofcollateral compensative arery.