Sharma M, Smith EE, Pearce LA, et al. - The majority of patients with embolic stroke of undetermined source (ESUS), including those who had never had a clinical stroke or a transient ischemic attack, had multiple large and/or cortical brain infarcts detected by MRI, indicating a significant burden of clinical stroke and covert brain infarction. Multiple vascular territories were commonly involved in infarcts.

• The mean age of the 918 substudy cohort members was 67 years, and 60% were men, with a median of 64 days between the qualifying ischemic stroke and MRI.

• On MRI, 855 (93%) had recent or chronic brain infarcts, 646 (70%) had multiple infarcts, and 62% (401/646) had multiple arterial territories involved.

• Multiple brain infarcts were found in 68% (510/755) of patients who had no history of stroke or transient ischemic attack prior to the qualifying ESUS.

• Prior stroke/TIA, modified Rankin Scale score >0, and current tobacco use were all linked to multiple infarcts.

• Topographically, large and/or cortical infarcts were present in 89% (757/855) of patients with infarcts, while infarcts were solely tiny and subcortical in 11% (98/855).

• Data reported that 57% (251/437) of patients with multiple major and/or cortical infarcts had one or more involving a different vascular territory from the qualifying ESUS.