Acute Cerebral Microinfarcts in Acute Ischemic Stroke: Imaging and Clinical Significance

<b><i>Background:</i></b> Limited data exist on the significance of acute cerebral microinfarcts (A-CMIs) in the context of acute ischemic stroke (AIS). We aimed to determine the profile and prognostic significance of A-CMIs on magnetic resonance imaging (MRI) in patients presenting with AIS. <b><i>Methods:</i></b> A prospective single-center series of patients with AIS who had 3T MRIs between March 2013 and December 2019. The presence, number, and location of A-CMIs on diffusion-weighted imaging, and markers of cerebral small vessel disease (CSVD), macroinfarcts features, and etiology were classified as cardioembolism (CE) or large artery atherosclerosis (LAA) or none. <b><i>Results:</i></b> Among 273 patients, A-CMIs were detected in 130 patients (47.6%), of whom cortical A-CMIs were found in 95 (73.0%) patients. Patients with A-CMIs were significantly older, less likely to have diabetes mellitus, and more likely to have atrial fibrillation and an embolic source (CE or LAA) compared to other patients. Patients with A-CMI had a higher frequency of macroinfarcts (diameter &#x3e;20 mm), more often multiple and distributed in single or multiple vessel territories than other patients. An embolic source (LAA or CE) was independently associated with cortical A-CMIs (LAA adjusted odds ratio [aOR] 4.0 95% confidence interval [CI] 1.6–9.5; CE aOR 2.5, 95% CI 1.1–5.6), whereas lacunes were independently related to subcortical A-CMIs (aOR 2.6, 95% CI 1.2–5.8). <b><i>Conclusions:</i></b> We have shown A-CMIs occur in cortical and subcortical regions in nearly half of AIS patients, where microembolism and CSVD are, respectively, the key presumed etiological mechanism.