Supplementary Material for: Towards Understanding the Cause of Stroke in Young Adults Utilising a New Stroke Classification System (A-S-C-O)

Background: Stroke in younger people is relatively common and frequently unexplained. While understanding of the causes of young stroke has improved, there remains uncertainty over the role of low-risk lesions such as a patent foramen ovale (PFO). The TOAST criteria are often used to describe stroke aetiology, but in younger people in whom PFOs are frequent, there is a very high proportion of cases attributed to cardiac embolism. The impact of using the newer A-S-C-O criteria on stroke aetiology was investigated. Methods: Consecutive patients with ischaemic stroke were investigated and categorised by the TOAST and ASCO1 criteria. Stroke aetiology was presented and compared by the different classification systems. Results: Of the 106 ischaemic stroke cases, by TOAST 6% were ‘large artery atheroma’, 11% ‘small vessel occlusion’, 28% ‘cardioembolic’, 22% ‘other determined cause’ and 33% ‘undetermined cause’. The vascular territory and associated causes are presented. With the ASCO1 criteria, there were more cases of unclassified stroke (51.9 vs. 34.0%; p Conclusion: Using the ASCO criteria, more patients fall into the undetermined group which more accurately reflects our current uncertainty regarding the pathogenic relevance of PFOs in this age group.