The ASCOD classification system ¹, published in 2013, aims to define phenotypes of ischaemic strokes for individual patients by assigning a degree of probability to each of the most common causes of this pathology.

It serves most strictly as a research tool but is also useful clinically as a mnemonic to consider common causes of ischaemic stroke.

Compared to alternative classification systems that assign only one cause to each individual stroke and often have an "undefined" category, the ASCOD system allows classification of each stroke by detailing multifactorial causes and their relative probability of causation.

Classification

The ASCOD classification, not fully detailed here, offers objective criteria for each of the following diseases based on imaging, laboratory and clinical evaluations:

• atherosclerosis/atherothrombosis

  • includes criteria such as stenosis >50% of an artery supplying the ischaemic territory, endoluminal thrombus or occlusion

• small-vessel disease

  • includes criteria such as lacunar infarcts, leukoaraiosis and microbleeds

• cardiac pathology

  • includes findings such as mitral stenosis, recent myocardial infarction, documented atrial fibrillation, endocarditis

• other causes

  • amongst others: dolichoectasia with complicated aneurysm, systemic lupus, antiphospholipid antibody syndrome, sickle cell disease, moyamoya disease​

• dissection

  • ideally documented with MRI or CT

Grading

For each letter in the system, a grade is assigned:

• 1: the disease is present and can potentially be a cause

• 2: the disease is present, but the causal link is uncertain

• 3: the disease is present, but the causal link is unlikely

• 0: the disease is absent

• 9: the workup is insufficient to grade the disease

History and etymology

The ASCOD classification replaces the ASCO classification ² published in 2009, with the addition of the letter "D" to take into account the importance of arterial dissection in the genesis of ischaemic stroke, particularly in young patients.