Accidental microembolic signals: prevalence and clinical relevance

Background: The purpose of this study was to examine the occurrence of accidental microembolic signals (MES) and its clinical relevance in patients receiving routine transcranial Doppler (TCD) examinations. Methods: We retrospectively reviewed our institutional TCD database (from January 2007–November 2012). The arteries with positive MES, the presumed sources of emboli and the clinical backgrounds were analyzed. Results: A total of 10,067 patients received routine TCD examinations in our laboratory during the research period. MES were detected in 98 arteries of 78 patients, with a frequency of 0.77 % of all the recruited patients. A high percentage of MES (64.3 %) were detected in MCAs. Sixty five (83.33 %) accidental emboli were from arterial sources, including atherosclerotic cerebral or carotid artery stenosis (n = 45), moyamoya disease (n = 11), intracranial arteries (n = 3) and Takayasu arteritis (n = 3). Thirteen (16.67 %) emboli were from cardiac sources, including atrial fibrillation (n = 3), artificial valves (n = 8), infective endocarditis (n = 2), patent foramen ovale (n = 2), and systemic lupus erythematosus (n = 1). In artificial valves disease, all patients with MES were asymptomatic, while in atherosclerotic cerebral or carotid artery stenosis, 66.67 % (n = 30) patients with MES were symptomatic. In different diseases with accidental MES, the proportion of symptomatic patients and asymptomatic patients were different (p < 0.001). Conclusions: MES are not uncommon during routine TCD examinations, the clinical value of which varied in different diseases.