SSS-TOAST CLASSIFICATION OF ISCHEMIC STROKE

• occlusion or stenosis ≥50% (according to NASCET) caused by atherosclerosis in relevant extra-/intracranial arteries
• history of ≥ 1 TIA/stroke within the territory of the index artery affected by atherosclerosis, occurring within the past month

OR

• evidence of near-occlusive stenosis or non-chronic total occlusion, determined to result from atherosclerosis, in relevant extra-/intracranial arteries (excluding the vertebral arteries)

OR

• the presence of ipsilateral border-zone infarctions (BZI) or multiple, temporally separated infarcts occurring within the region supplied by the affected artery

• atherosclerotic plaque causing stenosis <50% without any detectable plaque ulceration or thrombosis in a relevant extra-/intracranial artery
• history of ≥ 2 TIAs/strokes in the territory of index artery affected by atherosclerosis; at least one event occurring within the past month

OR

• evidence of extensive artery atherosclerosis in the absence of a complete diagnostic workup for alternative causative mechanisms

The presence of a high-risk cardiac source of cerebral embolism

• left atrial/ventricular thrombus
  
• (paroxysmal) atrial fibrillation/flutter
• sick sinus syndrome (SSS)
  
• recent myocardial infarction (< 1 month)
• bioprosthetic and mechanical valves
• rheumatic mitral or aortic valve disease
• symptomatic congestive heart failure with EF < 30%
• dilated cardiomyopathy
• nonbacterial thrombotic endocarditis
• an intracardiac tumor (such as papillary fibroelastoma or myxoma)

• evidence of systemic embolism

OR

• presence of multiple acute infarcts occurring in close temporal relation within the 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 could potentially lead to multifocal ischemic lesions, such as vasculitides, vasculopathies, and hemostatic or hemodynamic disturbances, are not present

• the presence of a cardiac condition associated with low or uncertain risk of cerebral embolism
  • mitral annular calcification
  • patent foramen ovale (PFO) +/- atrial septal aneurysm
  • left ventricular aneurysm without thrombus
  • isolated left atrial smoke (no mitral stenosis or atrial fibrillation)
  • complex atheromatous plaque located in the ascending aorta or proximal arch  (in CISS classification, such lesion is assigned to LAA)

OR

• evidence of obvious cardio-aortic embolism in the absence of a complete diagnostic workup for other potential causes

• imaging evidence of a single, clinically relevant acute infarct < 2 cm in greatest diameter within the territory of the penetrating arteries 
  
• absence of significant pathology in the parent artery at the site of the origin of the penetrating artery (most commonly ostial atheroma, less commonly parent vessel dissection, vasculitis, vasospasm, etc.); parent artery pathology is also referred to as branch artery disease (BAD) / branch occlusive disease (BOD) and is classified as TOAST 1 
  
  • diagnosis is based on high-resolution MRI   [Petrone, 2016]
  • more likely in younger patients
  • infarct is usually larger than a typical arteriolopathic stroke and is typically located in the pons    [Zhou, 2018]

• stereotypic lacunar TIAs within the past week
• clinical presentation of a classic lacunar syndrome

• classical lacunar syndrome in the absence of imaging sensitive enough to detect small infarctions

OR

• evidence of small artery occlusion in the absence of complete diagnostic assessment for other potential mechanisms

• presence of a specific disease process involving clinically relevant cerebral arteries (→ TOAST classification)

• a specific disease process that has occurred in close temporal or spatial relationship to the of onset stroke (e.g., arterial dissection, cardiac or vascular surgery, and cardiovascular procedures

• evidence for an evident other cause in the absence of complete diagnostic investigation for mechanisms listed above