Prevalence and prognostic impact of microembolic signals in arterial sources of embolism - A systematic review of the literature

Objective To compile available studies using microembolic signal (MES) detection by transcranial Doppler sonography in varying sources of arterial brain embolism. We investigated prevalences of MES and whether MES detection is of proven use for risk stratification. Method Studies reporting prevalences of MES and the risk of cerebral ischemic events were pooled for patients with symptomatic or asymptomatic carotid stenosis, intracranial artery stenosis, cervical artery dissection, and aortic embolism. Results MES were reported in 43% of 586 patients with symptomatic and in 10% of 1066 patients with asymptomatic carotid stenosis. Presence of one MES indicated an increased risk of future events [odds ratio (OR): 7.5, 95% confidence interval (Cl): 3.6-15.4, p < 0.0001 for symptomatic, and OR: 13.4, 95% CI: 6.5-27.4, p < 0.0001 for asymptomatic disease). MES were reported in 25% of 220 patients with symptomatic vs. 0% of 86 patients with asymptomatic intracranial stenosis (p < 0.000 1), Of 82 patients with cervical artery dissection presenting with TIA or stroke, 50% had MES compared with 13% of 16 patients with local symptoms (p = 0.006), In patients with aortic embolism, patients with plaques >= 4 mm more frequently had MES compared with patients with smaller plaques (p = 0.04), Data were insufficient to reliably predict future events in patients with intracranial stenosis, cervical artery dissection, and aortic embolism. Conclusion MES are a frequent finding in varying sources of arterial brain embolism, MES detection is useful for risk stratification in patients with carotid stenosis.