Clinical Significance of Microembolic Signal Detection in Acute Ischemic Stroke: Insights Into Ongoing Cerebral Embolization and Occult Etiologies

BACKGROUND AND PURPOSE: Transcranial Doppler (TCD) detects microembolic signals (MES), reflecting ongoing cerebral embolization. MES have been studied across stroke subtypes and may clarify etiology, monitor treatment, and predict recurrence. We aimed to determine the prevalence of MES in acute ischemic stroke (AIS), explore clinical and laboratory associations, and assess their role in etiological workup. METHODS: We conducted a prospective single-center study over 3 years including anterior circulation AIS patients within 24 h of onset. Stroke subtype was classified by TOAST criteria. Bilateral middle cerebral artery TCD monitoring was performed for 30 min to detect and quantify MES. RESULTS: Among 136 patients (mean age 60.1 ± 12.4 years), MES were detected in 22 (16.2%; 95% CI: 10.4%-23.5%). MES(+) patients had more often multiple-territory infarcts (36.4% vs. 10.5%, p = 0.005), newly detected atrial fibrillation (13.6% vs. 0.9%, p = 0.013), and cancer-associated stroke (18.2% vs. 0.9%, p = 0.002), whereas cryptogenic etiology was less common (18.2% vs. 41.2%, p = 0.041). MES were absent in lacunar stroke. MES positivity correlated with higher D-dimer levels (median 932 vs. 456 ng/mL, p < 0.001), and MES counts correlated strongly with D-dimer values (Spearman coefficient: 0.393, p < 0.001). CONCLUSIONS: MES were detected in one-sixth of anterior circulation AIS patients, but were absent in lacunar stroke. Their presence was associated with multiple-territory infarcts, newly detected atrial fibrillation, and cancer-related stroke. MES counts correlated with D-dimer levels, supporting their role as markers of ongoing cerebral embolization and underlying prothrombotic state, with potential utility in revealing occult embolic mechanisms.