Elena Zapata-Arriaza, MD
@ElenaZaps
Collateral status has been related to impact on infarct size after ischemic stroke (IS) recanalization. However, the smaller final infarct size is not always related to a good clinical situation, which seems to be related to the eloquence of the affected area, rather than the volume of the ischemic area itself. The present scientific work aims to evaluate the relation between collateral status and reperfusion degree on final infarct distribution and clinical outcome after IS due to large vessel occlusion (LVO).
Al-Dasuqi and colleagues performed a single center retrospective analysis of all patients with LVO who were treated with endovascular treatment between 2013-2019. The authors collected clinical, demographic and radiological data. They applied a multivariate voxel-wise general linear model to correlate the distribution of final infarction with collateral status and degree of reperfusion. Early favorable outcome was defined as a discharge modified Rankin Scale score ≤2.
Among all relevant results, it is relevant to highlight that poor collateral status was associated with infarction of MCA territory cortex and subcortical white matter tracts, as well as the MCA border zones, whereas higher mTICI (2b-3) preserved deep white matter and internal capsule (posterior limb) from infarction. In addition, the voxel-wise analysis showed that the presence of final infarct lesions in the left precentral gyrus and insula as well as right caudate nucleus was related to worse discharge mRS scores. In multivariate regression models, both mTICI and collateral status were among independent predictors of final infarct volumes. However, mTICI, but not collateral status (P=0.058), predicted favorable outcome at discharge.
Collaterals seem to play a fundamental role in the final size of the infarct; however, the presence of better collaterals prior to EVT does not ensure a better functional prognosis, although they are related to smaller ischemic volumes. Collaterals are essential to increase the time that the brain is able to tolerate hypoperfusion, but without sufficient recanalization (TICI 2b-3), the work of these collaterals will be in vain. This hypothesis could explain the results of the present study in which a better mTICI as opposed to robust collaterals, is related to a good functional prognosis. Furthermore, this work contributes to the growing evidence on the importance of infarct location. It is possible that the functional eloquence of certain areas could more clearly impact the prognosis of a stroke patient, regardless of its extent. Ultimately, this work shows us that maintaining or achieving a good collateral state will allow us to improve tolerance to ischemia in a patient with LVO, which may be transferred for mechanical thrombectomy (drip and ship model). However, what will increase the chances of an optimal clinical improvement will be the recanalization of the occluded vessel.
Finally, the results of this work open the way to change the radiological model of patient selection for EVT. Should we continue to select patients based on a cut-off point on the ASPECTS scale? Could a patient with low ASPECTS benefit from EVT if areas of functional eloquence are respected? No decision should be considered in isolation. The future of the radiological paradigm in stroke is promising and will allow us to improve the resources we offer to our patients.
