Cryptogenic stroke-the appropriate diagnostic evaluation

Ischemic strokes are a significant cause of morbidity and mortality in the United States. They may be due to large artery atherosclerosis, small vessel occlusion, cardioembolism, or other less common mechanisms such as toxins, hypercoagulable disorders, and vasospasm. Each mechanism carries its own risk of recurrence and prognosis. Strokes without an identifiable cause despite a complete work-up are described as cryptogenic. Cryptogenic stroke therefore is a diagnosis of exclusion, and one that should not be arrived at haphazardly. One must complete a thorough, and frequently challenging, stroke work-up prior to this diagnosis. Challenges in determining stroke etiology include the transient nature of precipitating events such as vasospasm or cardiac arrhythmias, variable durations of cardiac monitoring, and unclear significance of certain cardiac structural anomalies. Many consider cryptogenic stroke to be a heterogeneous combination of paroxysmal and occult conditions that create such diagnostic difficulties. The diagnosis of cryptogenic stroke itself carries with it specific outcomes and prognosis. This article will provide an overview of the definition and epidemiology, recommendations for diagnostic evaluation, and risks of recurrence of cryptogenic stroke.