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Micro-Embolic Signals and Dissection: Association or Causation for Stroke? A Systematic Review and Meta-Analysis

Background and Objective: Although the mechanism of stroke in cervical artery dissection (CAD) has been hypothesized to be embolization rather than hemodynamic compromise, there are a limited number of studies supporting this hypothesis. Detection of micro-embolic signals (MESs) using transcranial Doppler (TCD) helps in understanding the mechanism in these patients. A systematic review and meta-analysis were performed to estimate the prevalence of MES and its association with stroke outcomes in patients with acute stroke/TIA secondary to dissection. Methods: A comprehensive literature search was conducted for studies before January 26, 2021, in PubMed, Embase, Google Scholar, Cochrane Library, and ClinicalTrials.gov. Studies were identified that used TCD to detect MES in stroke/TIA patients secondary to CAD. Pooled prevalence was calculated. Entire statistical analysis was conducted in R version 3.6.2. Results: Eleven studies involving 112 patients (50 MES+, 62 MES−) were included in our meta-analysis. The pooled prevalence of MES among acute stroke/TIA patients secondary to dissection was 46.0% (95% CI 26.0–67.0%). The presence of MES was associated with an increased risk of early ischemic recurrence in patients with CAD. We could not estimate the functional outcome and mortality associated with the presence of MES due to the scarcity of data. Conclusions: Our meta-analysis showed 46% prevalence of MES in the studies which looked at acute stroke/TIA secondary to CAD using TCD. This finding supports the assumption that embolism may be a major cause of stroke in patients with dissection although this could be determined only in a small population.