Abstract: Background: Monitoring microembolic signals (MES) in patients with brain stem infarction has not been reported in the literature. This study aimed to investigate the relation between the presence of MES and vertebrobasilar artery (VBA) stenosis. Methods: The study included 156 patients with acute brain stem infarction who underwent detection of MES at the VBA through the occipital window using transcranial Doppler (TCD) ultrasonography. Results: MES were present in 20 (12.8%) patients. Clinical characteristics and laboratory parameters of the MES-positive and MES-negative groups did not differ significantly. Intracranial VBA stenosis was found to be an independent risk factor for MES [odds ratio (OR), 9.73; 95% confidence interval (CI), 1.34–81.46; p=0.038]. Patients with severe VBA stenosis had a higher prevalence of MES than those with moderate VBA stenosis (OR, 9.76; 95% CI, 1.53-80.12; p=0.040). VBA stenosis was found in 86 patients. The MES-positive group had more infarctions than the MES-negative group (p=0.014). Conclusion: VBA stenosis is the primary source of microemboli in patients with acute brain stem infarction. Microemboli originating from VBA stenosis are the cause of multiple infarctions.

Key words: Keywords: Brain stem infarction, vertebrobasilar stenosis, microembolic signal, transcranial Doppler ultrasonography