Stroke mechanism | Level of confidence | Criteria |
Large artery atherosclerosis | Evident | 1. Either occlusive or stenotic (≥50 percent diameter reduction or <50 percent diameter reduction with plaque ulceration or thrombosis) vascular disease judged to be caused by atherosclerosis in the clinically relevant extracranial or intracranial arteries, and |
2. The absence of acute infarction in vascular territories other than the stenotic or occluded artery | ||
Probable | 1. History of ≥1 transient monocular blindness (TMB), TIA, or stroke from the territory of index artery affected by atherosclerosis within the last month, or | |
2. Evidence of near-occlusive stenosis or nonchronic complete occlusion judged to be caused by atherosclerosis in the clinically relevant extracranial or intracranial arteries (except for the vertebral arteries), or | ||
3. The presence of ipsilateral and unilateral internal watershed infarctions or multiple, temporally separate, infarctions exclusively within the territory of the affected artery | ||
Possible | 1. The presence of an atherosclerotic plaque protruding into the lumen and causing mild stenosis (<50 percent) in the absence of any detectable plaque ulceration or thrombosis in a clinically relevant extracranial or intracranial artery and history of ≥2 TMB, TIA, or stroke from the territory of index artery affected by atherosclerosis, at least one event within the last month, or | |
2. Evidence for evident large artery atherosclerosis in the absence of complete diagnostic investigation for other mechanisms | ||
Cardio-aortic embolism | Evident | The presence of a high-risk cardiac source of cerebral embolism |
Probable | 1. Evidence of systemic embolism, or | |
2. The presence of multiple acute infarctions that have occurred closely related in time within both right and left anterior or both anterior and posterior circulations in the absence of occlusion or near-occlusive stenosis of all relevant vessels. Other diseases that can cause multifocal ischemic brain injury such as vasculitides, vasculopathies, and hemostatic or hemodynamic disturbances must not be present. | ||
Possible | 1. The presence of a cardiac condition with low or uncertain primary risk of cerebral embolism, or | |
2. Evidence for evident cardio-aortic embolism in the absence of complete diagnostic investigation for other mechanisms | ||
Small artery occlusion | Evident | Imaging evidence of a single and clinically relevant acute infarction <20 mm in greatest diameter within the territory of basal or brainstem penetrating arteries in the absence of any other pathology in the parent artery at the site of the origin of the penetrating artery (focal atheroma, parent vessel dissection, vasculitis, vasospasm, etc) |
Probable | 1. The presence of stereotypic lacunar transient ischemic attacks within the past week, or | |
2. The presence of a classical lacunar syndrome | ||
Possible | 1. Presenting with a classical lacunar syndrome in the absence of imaging that is sensitive enough to detect small infarctions, or | |
2. Evidence for evident small artery occlusion in the absence of complete diagnostic investigation for other mechanisms | ||
Other causes | Evident | The presence of a specific disease process that involves clinically appropriate brain arteries |
Probable | A specific disease process that has occurred in clear and close temporal or spatial relationship to the onset of brain infarction such as arterial dissection, cardiac or arterial surgery, and cardiovascular interventions | |
Possible | Evidence for an evident other cause in the absence of complete diagnostic investigation for mechanisms listed above | |
Undetermined causes | Unknown (no evident, probable, or possible criteria for the causes above) | Cryptogenic embolism: 1. Angiographic evidence of abrupt cut-off consistent with a blood clot within otherwise angiographically normal looking intracranial arteries, or 2. Imaging evidence of complete recanalization of previously occluded artery, or 3. The presence of multiple acute infarctions that have occurred closely related in time without detectable abnormality in the relevant vessels |
Other cryptogenic: Those not fulfilling the criteria for cryptogenic embolism | ||
Incomplete evaluation: The absence of diagnostic tests that, under the examiner's judgment, would have been essential to uncover the underlying etiology | ||
Unclassified | The presence of >1 evident mechanism in which there is either probable evidence for each, or no probable evidence to be able to establish a single cause |
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