Created 26/09/2022, last revision 22/02/2023

  • The SSS-TOAST classification is an evidence-based classification algorithm that reflects advances in stroke imaging and epidemiology [Ay, 2005]
  • based on certain clinical and imaging criteria, each TOAST subtype is divided into 3 subcategories “certain”, “probable”, or “possible”
  • the new algorithm refines the determination of the most likely etiology in the presence of multiple competing mechanisms
  • an automated web-based version of the SSS-TOAST, the Causative Classification System (CCS), was developed to facilitate its utility in multicenter settings (Ay, 2007)
    • CCS allows rapid analysis of patient data with excellent intra- and inter-examiner reliability when accurate subtyping is critical (trials)
    • the purple text was not present in the original SSS-TOAST publication in 2005

SSS-TOAST 1 – Large Artery Atherosclerosis (LAA)

  • occlusion or stenosis ≥50% (according to NASCET) or <50 % diameter reduction with plaque ulceration or thrombosis caused by atherosclerosis in the clinically relevant extra-/intracranial arteries


  • the absence of acute infarction in vascular territories other than the stenotic or occluded artery
Significant internal carotid artery stenosis on CTA
Large artery atherosclerosis (LAA)
  • occlusion or stenosis ≥50% (according to NASCET) caused by atherosclerosis in the clinically relevant extra-/intracranial arteries
  • history of ≥ 1 TIA/stroke from the territory of the index artery affected by atherosclerosis  within the last month


  • evidence of near-occlusive stenosis or non-chronic complete occlusion judged to be due to atherosclerosis in the clinically relevant extra-/intracranial arteries (except for the vertebral arteries)


  • the presence of ipsilateral border-zone infarctions (BZI) or multiple, temporally separate infarctions only within the territory of the affected artery
  • atherosclerotic plaque causing stenosis <50% in the absence of any detectable plaque ulceration or thrombosis in a clinically relevant extra-/intracranial artery
  • history of ≥ 2 TIAs/strokes from the territory of index artery affected by atherosclerosis; at least 1 event within the last month


  • evidence of extensive artery atherosclerosis in the absence of complete diagnostic investigation for other mechanisms

SSS-TOAST 2 – Cardioaortic embolism


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

  • left atrial/ventricular thrombus
  • (paroxysmal) atrial fibrillation/flutter
  • sick sinus syndrome
  • recent myocardial infarction (< 1 month)
  • bioprosthetic and mechanical heart valves
  • rheumatoid mitral or aortic valve disease
  • chronic myocardial infarction together with low ejection fraction (< 28%]
  • symptomatic congestive heart failure with EF < 30%
  • dilated cardiomyopathy
  • nonbacterial thrombotic endocarditis
  • an intracardiac tumor (papillary fibroelastoma, myxoma)
  • evidence of systemic embolism


  • 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
  • the presence of a cardiac condition with a low or uncertain risk of cerebral embolism
    • mitral annular calcification
    • mitrální anulární kalcifikace
    • patent foramen ovale (PFO) +/- atrial septal aneurysm
    • left ventricular aneurysm without thrombus
    • isolated left atrial smoke (no mitral stenosis or atrial fibrillation
    • komplexní plát v ascendentní aortě nebo oblouku aorty
    • complex atheroma in the ascending aorta or proximal arch (in CISS classification, such lesion belongs to LAA)


  • evidence of obvious cardio-aortic embolism in the absence of complete diagnostic investigation for other mechanisms

SSS-TOAST 3 – Small-artery occlusion

  • imaging evidence of a single, clinically relevant acute infarction < 2 cm in greatest diameter within the territory of penetrating arteries  Lacunar infarct in the left thalamus (DWI)
  • absence of significant pathology in the parent artery at the site of the origin of the penetrating artery (most commonly junction focal atheroma, less frequently 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  Penetrating artery disease with a parent artery atherosclerosis

    • diagnosis 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 Probable Branch Artery Disease (BAD) leading to pontine infarct. CTA revealed no major stenosis in posterior circulation. HR-MRI is not available.  [Zhou, 2018]
  • stereotypic lacunar TIAs within the past week
  • presence of a classical lacunar syndrome
  • classical lacunar syndrome in the absence of imaging that is sensitive enough to detect small infarctions


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

SSS-TOAST 4 – Other causes

  • presence of a specific disease process that involves clinically appropriate brain arteries
  • a specific disease process that has occurred in clear and close temporal relation to the onset of brain infarction, such as arterial dissection, cardiac or arterial surgery, and cardiovascular interventions
  • evidence for an evident other cause of stroke in the absence of complete diagnostic evaluation for mechanisms listed above

SSS-TOAST 5 – Undetermined causes

  • cryptogenic embolism → ESUS criteria

    • vessel imaging findings suggesting embolic etiology:
      • evidence of abrupt cutoff consistent with a blood clot within otherwise angiographically normal-looking intracranial arteries
      • evidence of complete recanalization of the previously occluded artery
      • presence of multiple acute infarctions that have occurred closely related in time without detectable abnormality in the relevant vessels
  • other cryptogenic strokes – those not fulfilling the criteria for cryptogenic embolism
  • incomplete evaluation – the absence of diagnostic tests that would have been essential to uncover the underlying cause
  • unclassified – the presence of >1 evident mechanism; either there is probable evidence for each, or no single cause can be reliably established

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SSS-TOAST classification