Intracranial Arterial Stenosis Microembolization And Hemodynamics

Part1Microembolic Signals Predict Cerebral Ischemic Events in Patients with Moyamoya DiseaseBackground:Recent studies found that microembolic signals (MES) could be detected by transcranial Doppler in patients with moyamoya disease. However the clinical significance of MES in moyamoya disease remains unclear.Objective:We aimed to investigate whether the MES could predict cerebral ischemic events in patients with moyamoya disease.Methods:Fifty-four consecutive patients with moyamoya disease were recruited. MES were monitored by transcranial Doppler for30minutes in bilateral middle cerebral arteries of each patient on admission. Patients were followed up for1year. The primary endpoint was cerebral ischemic events including stroke and transient ischemic attack (TIA).Results:MES were detected in11(20.4%) patients, with a frequency of11(10.2%) in108hemispheres. Logistic regression analysis revealed that previous ischemic events within3months was associated with the presence of MES (OR=4.41,95%CI1.11-17.59). During median follow-up of384days,14(13.0%) hemispheres had ischemic events (7strokes and7TIAs). Cox regression showed that the hazard ratio for the risk of new ischemic stroke and TIA in the hemispheres with MES was6.84(95%CI1.82-25.66) compared with those without, and10.61(95%CI1.66-67.70) for ischemic stroke alone, after controlling for age, sex, presence of ischemic events at baseline, Suzuki stages and revascularization surgery.Conclusions:In patients with moyamoya disease, the presence of MES is associated with recent ischemic symptoms, and independently predict cerebral ischemic events. MES detection may be of potential clinical value in the management of patients with MMD. Part2Impaired Dynamic Cerebral Autoregulation in Moyamoya DiseaseBackground:Moyamoya disease (MMD) can lead to deficit of cerebral autoregulation, thus may increases the risk of cerebral ischemia and hemorrhage. It is desirable to know when this protective mechanism begins to impair and how it changes as MMD progress.Purpose:We applied a non-invasive method to investigate the status of autoregulation at different stages of MMD.Methods:This study investigated26hemispheres with MMD amongl3patients and20hemispheres without stenosis amonglO controls. Degree of distal carotid artery stenosis was classified according to modified Suzuki stage. Cerebral autoregulation was assessed by transfer function analysis from spontaneous oscillations of cerebral blood flow velocity and blood pressure.Results:Three autoregulatory parameters, the rate of recovery (RoRc), phase shift, and gain were derived from transfer function. RoRc and phase shift estimated from the first stage are significantly different from controls (RoRc22.70±4.93%/s VS.40.78±20.92%/s, p<0.05; phase35.20±12.29°VS.60.01±18.96°, p<0.05).Gain and coherence becomes significantly different when MMD develops to stage II(gain0.40±0.16VS.0.86±0.50,p<0.05; coherence0.64±0.11VS.0.42±0.16,p<0.05).RoRc (r=-0.478, p<0.05), phase (r=-0.619, p<0.001)and gain (r=-0.507, p<0.001) are all significantly correlated with the angiographic stages.Conclusions:Cerebral autoregulation starts to impair at early stage of MMD. And autoregulatory parameters are highly correlated with the stages, suggesting the dysautoregulation may tend to worsen gradually with progression of MMD. Part3Impaired Dynamic Cerebral Autoregulation and Cerebrovascular Reactivity in Middle Cerebral Artery StenosisBackground:A number of studies reported that stenosis in internal carotid artery may impair cerebral hemodynamics, including cerebral autoregulation and cerebrovascular reactivity (CVR), which increases the risk of cerebral ischemic events. And intracranial artery occlusive diseases, especially middle cerebral artery (MCA) stenosis, are major causes of ischemic stroke in Chinese populations. However such studies in intracranial artery stenosis are lacking.Purpose:We sought to investigate the capacity of cerebral autoregulation and CVR in patients with MCA stenosis.Methods:Twenty-one patients with MCA stenosis diagnosed by magnetic resonance angiography and15healthy controls were enrolled. Cerebral autoregulation was assessed by autoregulatory parameters (rate of recovery/phase/gain) derived from transfer function from spontaneous oscillations of cerebral blood flow velocity and blood pressure. CVR was tested by a rebreathing maneuver.Results:Rate of recovery, phase and CVR estimated from moderate MCA stenosis (rate of recovery=17.76±8.21%/s, phase=26.93±15.67°,and CVR=1.53±0.84%/mmHg, respectively) were significantly different (p<0.05) from controls (rate of recovery=39.62±27.99%/s, phase=55.66±22.1°, and CVR=2.18±0.80%/mmHg, respectively). Rate of recovery (r=-0.698, p<0.001), phase (r--0.738, p<0.001)) and CVR (r=-0.690, p<0.001) were all significantly correlated with the degree of stenosis.Conclusion:Cerebral autoregulation and CVR were impaired in patients with≥50%MCA stenosis. The measures of both hemodynamic properties were inversely correlated with the stenotic degree.