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Cryptogenic stroke

Shyam Prabhakaran, MD, MS
Mitchell SV Elkind, MD, MS, FAAN
Section Editor
Scott E Kasner, MD
Deputy Editor
John F Dashe, MD, PhD


The majority of ischemic strokes are due to cardioembolism, large vessel atherothromboembolism, small vessel occlusive disease, or other unusual mechanisms. However, many ischemic strokes occur without a well-defined etiology and are labeled as cryptogenic.

This topic will provide an overview of cryptogenic stroke. A discussion of stroke classification and the clinical diagnosis of stroke subtypes is found separately. (See "Etiology, classification, and epidemiology of stroke" and "Clinical diagnosis of stroke subtypes".)


In its most useful clinical sense, the term cryptogenic stroke designates the category of ischemic stroke for which no probable cause is found despite a thorough diagnostic evaluation [1].

The cryptogenic stroke category was devised first, for research purposes, in the NINDS Stroke Data Bank [2,3] and later modified in the TOAST trial [4]. Classification along these lines has become increasingly used in clinical practice, as optimal management relates to the underlying mechanism. (See "Etiology, classification, and epidemiology of stroke", section on 'TOAST classification'.)

By the TOAST classification (table 1), which is the one most commonly used in clinical practice, cryptogenic stroke (or stroke of undetermined origin in TOAST terminology) is defined as brain infarction that is not attributable to a source of definite cardioembolism, large artery atherosclerosis, or small artery disease despite a standard vascular, cardiac, and serologic evaluation. The category of stroke of undetermined etiology in the TOAST classification includes patients with less well-established potential causes of cardiac embolism, such as patent foramen ovale, aortic arch atheroma, and mitral valve strands, as well as potential prothrombotic disorders; stroke of undetermined etiology also includes patients with two or more equally plausible identified causes of stroke [4].

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Literature review current through: Nov 2017. | This topic last updated: Feb 12, 2017.
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