Stroke is a common source of morbidity and mortality in the United States. Between 20% and 25% of strokes occur in patients with a previous stroke or transient ischemic attack. More than 90% of the global stroke burden can be traced to the modifiable risk factors of blood pressure, diet, physical inactivity, smoking, and abdominal obesity. The American Heart Association and American Stroke Association (AHA/ASA) published updated guidelines for preventing recurrent ischemic stroke, focusing on overall cardiovascular risk reduction and targeted secondary prevention.

Stroke Subtype Classification

Ischemic strokes account for nearly 90% of strokes in the United States. The TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification scheme groups ischemic strokes into lacunar or nonlacunar subtypes. Lacunar strokes present with a specific syndrome pattern and can have normal imaging or subcortical ischemic areas less than 0.6 in (1.5 cm) in diameter.

Nonlacunar strokes can be caused by cardioembolism, large artery atherosclerosis, and cryptogenic sources. Cardioembolic sources are suggested when previous or current ischemia occurs in multiple vascular territories. Large artery atherosclerotic lesions may present with cortical, brainstem, cerebellar, or larger subcortical areas of ischemia. Cryptogenic strokes defy characterization despite complete evaluations and again subdivide into embolic or nonembolic strokes of uncertain source. Embolic strokes of an uncertain source are nonlacunar and appear embolic, but no source of embolus can be identified. Figure 1 details the relative frequency of different stroke subtypes.