Transcranial Doppler ultrasound (TCD) can detect circulating microembolic signals (MES) from a variety of embolic sources. We mentioned about MES detection by TCD, MES detection in patients with ischemic stroke, and tail signs (TS) . A prevalence of MES of 5.7% was found in 151 consecutive patients with ischemic stroke. TCD was useful to confirm the stroke mechanism and to predict individual prognosis in some patients. The prevalence of MES was low and TCD did not always detect MES in patients with ischemic stroke. Our attention also focused on TS, which appeared as a small reversal signal after MES on the high time resolution spectral display. MES and artifacts were examined in experimental animals to determine whether TS were specific changes associated with MES, and TS were investigated in both animal and clinical studies. TS associated with MES were observed in both animal and clinical studies, and were never associated with artifacts. These results indicate that TS are highly specific for MES and can be used as another criterion for MES identification.
