Acute ischemic stroke (AIS) is a leading cause of adult mortality and morbidity in the United States, affecting over 800,000 individuals, annually, leaving many with permanent disability. Furthermore, hundreds of thousands of Americans experience a transient ischemic attack (TIA), a momentary episode of neurologic dysfunction, which often precedes a major stroke and serves as a warning for future ischemic events. Despite symptoms resolving, experiencing a TIA increases the risk of stroke by 20% within 90 days. Emergent evaluation, prompt acute treatment, and identification of stroke etiology for secondary prevention are key to decreasing the morbidity and mortality associated with cerebrovascular disease. Key to treatment and prevention is the identification of stroke etiology - large vessel atherosclerosis, cardioembolic phenomenon, or in-situ small vessel cerebrovascular disease - since primary and secondary prevention measures differ based on stroke subtype. The diagnosis of ischemic stroke includes a combination of patient history, clinical assessment, and brain imaging. However, identifying the cause of cerebrovascular ischemia is challenging and routinely assigned of cryptogenic origin.