"Tail sign" associated with microembolic signals

Background and Purpose-Transcranial Doppler ultrasound (TCD) can detect cir culating microembolic signals (MES). We focused our attention on tail signs (TS), a signal associated with MES that appeared as a small reversal signa l after MES on the high time resolution spectral display. We examined MES a nd artifacts in an animal study to determine whether TS were specific chang es associated with MES and investigated the characteristics of TS in both a nimal and clinical studies. Methods-In an animal study, adult pigs with venoarterial extracorporeal mem brane oxygenation and minimal anticoagulation therapy were used as a model for cerebral embolism. After performing TCD monitoring with a multigated ap proach, we did an offline analysis to investigate several parameters concer ning MES and TS. We also examined TS in patients in a clinical study. Results-From a total of 362 MES investigated in the animal study, 72.9% wer e followed by TS. We could not find any TS associated with artifacts. The t ime delay between TS and MES was negatively correlated with the velocity of MES. MES almost always appeared first in the proximal channel, whereas TS conversely appeared first in the distal channel. In the clinical study, we were also able to observe TS associated with MES. Conclusions-TS may represent emboli passing down a branch vessel or twisted downstream vessel, TS are specific for MES and can be used as another crit erion for MES identification.