It is a truism of vascular neurology that secondary prevention depends on the cause of an ischemic stroke. We revascularize those with extracranial carotid stenosis, we anticoagulate those with cardioembolic infarcts due to atrial fibrillation, and we treat with antibiotics those with infective endocarditis. Determining the etiologic subtype, or cause, of stroke is therefore rightly considered the main objective of the evaluation of the patient with stroke. Despite the central role of this evaluation, it is surprising that our ability to determine the cause of stroke in many cases is quite limited, and that the process of determining the etiology is so subjective. In many circumstances, we simply infer the cause of stroke from incomplete or inconclusive data or else choose from among several competing possibilities. Why, in an era of increasing rigor with regard to our standards for choosing therapies for stroke prevention, are we so at a loss when it comes to determining the cause of stroke in the first place?
Mitchell S. V. Elkind. Stroke Etiologic Classification—Moving From Prediction to Precision. JAMA Neurol. 2017;74(4):388–390. doi:10.1001/jamaneurol.2016.5926