Grant: CIHR Fellowship

In an acute ischemic stroke, occlusion of cerebral blood vessels prevents the critical flow of oxygen to the brain. Without rapid revascularization, the death of brain tissue subsequently occurs. Computed tomography perfusion (CTP) can be used to visualize this process in real-time. Ischemic core, defined as tissue that is no longer salvageable, can be visualized alongside ischemic penumbra, tissue at risk of death that may be saved with blood flow restoration. Over the past 5 years, clinical trials have utilized CTP to select patients with severe stroke to undergo rapid revascularization via mechanical clot retrieval. Patients with a small core and large penumbra have been found to benefit the most from these interventions while, in contrast, patients possessing a large ischemic core benefit less and are at an increased risk of life-threatening bleeding. Patients with a large ischemic core are therefore less likely to be offered therapy. There is a growing recognition that in some cases, CTP may actually overestimate ischemic core. This phenomenon, termed Ghost Ischemic Core (GIC), carries the risk of precluding patients from undergoing necessary clot retrieval. Why GIC occurs in some patients, but not in others, is unclear. We aim to explore this particular question by analyzing the prevalence, topography, and natural history of GIC in relation to baseline clinical presentation, interventions utilized, and overall outcomes. In doing so, we hope to identify patients and/or clinical scenarios where ischemic core may be at risk of overestimation and shed further light into why this issue occurs in the first place. With the use of CTP becoming mainstream worldwide, the findings of this study will have the potential to launch new initiatives to improve ischemic core estimation and provide practical information for clinicians assessing patients at the bedside.