E. B. Ringelshtein
University Hospital Münster, Department of Neurology – Münster, Germany

Microembolic signals (MES) detected by transcranial ultrasound have first been described in the 80ies by Merrill Spencer and have rapidly gained great importance for the exploration of the pathophysiology underlying various stroke etiologies. Finally, MES have been proven as a reliable biomarker concerning the prognosis of symptomatic and asymptomatic internal carotid artery (ICA) stenoses. Typical clinical indications for microembolus detection (MD), a time-consuming, investigator-dependent US technique, are monitoring of cardiac and carotid surgery, arterial interventions, detection of occult sources of embolism, defining the culprit in competing sources of embolism, development of less emboligenic surgical techniques and refined devices.

MES detection can also be helpful to evaluate decompression illness and fat embolism. The number of observational or even randomised prospective studies on MD has reached the number of nearly 400 (according to PubMed). MD is increasingly applied to aggressive interventions, and often combined with DWI and Flair MR-imaging of the brain. Nearly all types of mechanical or biological valves of the heart have been tested by means of MD, as well as the corresponding surgical or transarterial interventions. In mechanical valves gaseous microbubbles due to microcavitation are frequent – and harmless. Amazingly, only little is known about atrial fibrillation and MES. Three important randomised controlled trials, the CARESS, the ACES and the CLAIR-trial have been performed. They will also be reviewed, because they demonstrate the specific value of MD as surrogate endpoint for future strokes.

Key words: microembolus, review, ultrasound.

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