Danny R. Rose, Jr., MD
As the scope and availability of endovascular treatment for large vessel occlusions in patients with ischemic stroke continues to increase, it is important for providers to have the ability to screen and predict which patients will benefit from these therapies. The most effective approach has been a topic of much debate and research, including utilizing ancillary testing to account for individual variations in collateral circulation and other factors that could potentially extend treatment indications and predict outcomes. Nearly all endovascular treatment trials use some combination of noncontrast head CT (NCCT), CT angiography (CTA) and/or CT perfusion (CTP) imaging to assist in clinical decision making due to the speed and availability of such scans. However, recent studies found that the currently utilized modalities may be insufficient to predict treatment effect or outcome. Wijngaard et al. sought to use cortical venous filling (CVF), a potential marker for collateral extent and perfusion, to assess whether the extent or velocity of CVF as obtained through dynamic CTA predicts clinical outcome at 3 months in ischemic stroke patients with proximal middle cerebral artery occlusion.
All patients received a NCCT evaluated for early ischemic changes (ASPECTS); CTP/CTA was used for clot burden score, collateral status, cerebral-blood-flow (CBF), cerebral-blood-volume (CBV), mean-transit-time (MTT) and time-to-peak (TTP). Using the dynamic CTAHo, CVF was assessed visually—cortical venous contrast opacification and the number of cortical and anastomotic veins were evaluated in comparison with the contralateral hemisphere. The number of seconds to reach first CVF (appearance of any cortical vein draining into the superior sagittal sinus), optimal CVF (maximum contrast opacification of all cortical veins), and end of venous filling (complete absence of contrast) was measured. The velocity of CVF was calculated as the median differences between venous filling of the affected versus non-affected hemisphere. In addition, the extent of CVF was defined as either “good” or “poor,” based on comparing the extent of cortical vein filling at optimal CVF with the unaffected hemisphere using 50% as a cutoff.
This study represents a novel use of venous filling parameters in predicting clinical outcome after ischemic stroke, resulting in a more accurate prediction when used in combination with previously studied measures. Based on these preliminary findings, one of the more promising applications may be its utility in predicting treatment effect of mechanical thrombectomy, but the small number of patients examined requires evaluation in a larger, prospective trial. If supported in additional research, CVF has the potential to become an important part in future trial design with respect to selecting patients for endovascular intervention. The authors’ choice to utilize dynamic CTA, however, limits its widespread application, as the more ubiquitous single-phase CTA cannot obtain time-resolved measurements. Parameters designed for use in single-phase CTA could be evaluated in a future study for its potential utility in facilities without dynamic CTA.