Evaluation of the role of cerebral collaterals in acute ischaemic stroke due to large vessel occlusion

Objective: Stroke is a devastating neurological condition affecting over 150,000 people in the United Kingdom every year with an individual suffering a stroke approximately every three and a half minutes. The collateral circulation plays an important role in maintaining blood flow to the tissue that is at risk of developing ischaemia. The aim of my study was to assess the role of collaterals in the development of ischaemic tissue and in clinical outcome. Methods: Data was derived from a large international study (The SOS Trial: A Study of Survival and Outcome after Stroke ClinicalTrials.gov Identifier: NCT01193569). For all enrolled patients, functional outcome was defined by the modified Rankin Scale (mRS) determined at 90 days after the index event. Collaterals on CT-Angiography (CTA) were scored using the Tan score. This was correlated to development of ischaemic regions using the ASPECTS score as well as the clinical outcome score NIHSS. Results: My results show that an increasing TAN score appears to be associated with a lower mRS score (p=0.048; 95% CI). There was a positive correlation between ASPECTS score and Tan score (p=0.049). M2 and M4 regions were associated with an increase in NIHSS (p= 0.027; 0.009); M2 and M5 regions were associated with an increase in mRS (p= 0.019; 0.023). An increase in ASPECTS score (less damage) implied a reduction in the NIHSS and mRS score (better outcome). Conclusion: Our results have potentially a huge impact on patient selection, as they demonstrate that patients with good collaterals should be transferred for treatment to tertiary care centres for thrombectomy or patient selection according to the salvageability of specific functions. This will hopefully allow patients to have better outcomes after suffering a stroke and reduce morbidity and disability in the long term. More work is required to elucidate further prognostic markers for collateral formation and outcome.