Stroke of undetermined cause: workup and secondary prevention

Purpose of reviewThe purpose of this review is to update the reader on current concepts of workup and secondary prevention in patients with stroke of undetermined cause.Recent findingsClinical research in patients with cryptogenic stroke has been hampered by the lack of standardized, widely accepted diagnostic criteria. The new definition of Embolic stroke of undetermined etiology' postulates an embolic mechanism of ischemic stroke. It is based on the exclusion of lacunar infarction by brain imaging, arterial stenosis more than 50% or dissection of the respective brain-supplying artery by computed tomography/magnetic resonance-angiography or ultrasound, atrial fibrillation by at least 24h EKG monitoring, as well as some rare etiologies such as vasculitis, drug abuse, or coagulopathies. However, it still comprises many patients with atherosclerotic etiologies (but <50% stenosis) as well as covert paroxysmal atrial fibrillation which can be detected by repeated Holter EKG or an implantable device. A patent foramen ovale can be found in up to 58% of cryptogenic stroke patients, but causality in an individual patient remains uncertain and can only be statistically inferred.SummaryThe new concept of embolic stroke of undetermined etiology enabled three ongoing randomized controlled trials which investigate oral anticoagulation versus aspirin for secondary stroke prevention.