Response to the letter by Dr. Sharma

We thank Dr. Sharma for his important input. Dr. Sharma iscorrect in claiming that MES-detection looks only at one sideof the picture of stenotic or atherosclerotic artery disease,namely the embolic potential. He is also correct in claimingthattestingofthecerebro-vascularreservecapacity,evenwithtests aseasyto perform asthe breath-holdingindex, evaluatesthe hemodynamic component of stenosis much better. Fur-thermore, he is correct when he claims that a poor reservecapacity is of significance for the prediction of future strokerisk [1]. However, in our opinion, cerebro-vascular reservecapacity testing does not have the same importance as MES-detection,and there are evenmoredifficulties in assessing therisk of patients who have a poor reserve capacity and MES.First, it has been proven by MRI that ischemic strokesattributable to carotid stenosis are embolic and not hemo-dynamic in the vast majority of cases. Drawing from themore than 5,000 patients listed in the German stroke databank, Grau showed that among patients with significantmacroangiopathy, 90% had territorial and only 10% hadhemodynamic infarctions [2]. Furthermore, hemodynamiccompromise is not as frequent as one might think, even inhigh grade stenosis, due to the collaterals, which are usuallyeffective in the circle of Willis. Furthermore, the cerebro-vascualar reserve capacity has the tendency to improve withtime [3], which also sheds doubt on the prognostic signifi-cance of future events. Therefore, the association ofexhausted reserve capacity between future stroke risk isquite convincing from the studies published but much lessconvincing from pathophysiological considerations. Themajority of patients are endangered by the embolic potentialof stenosis and not by the hemodynamic compromise.Furthermore, the tests used to assess reserve capacity arequite heterogeneous, even more heterogeneous than themethods to detect MES. For our review on the prospectiverisk of MES in arterial sources of embolism [4], weencountered a number of methodological variations in thestudies that limited study comparability and made it quitehard to attribute a quantitative prospective risk. As Dr.Sharma writes, this is probably why the method is notoverall accepted as a screening tool and the reason why weset up the review as published. With odds ratios