Imaging the future of stroke: I. Ischemia

Abstract

Envisioning the future of stroke appears daunting considering the milestones already achieved in stroke imaging. A historical perspective on the developments in stroke care provides a striking narrative of how imaging has transformed diagnosis, therapy, and prognosis of cerebrovascular disorders. Multimodal imaging techniques such as CT and MRI, incorporating parenchymal depictions, illustration of the vasculature, and perfusion data, can provide a wealth of information regarding ischemic pathophysiology. Key elements of ischemic pathophysiology depicted with imaging include vascular occlusion, compensatory collateral flow, resultant hemodynamic conditions that reflect these sources of blood flow, and the neurovascular injury that ensues. The mantra of "time is brain" has been perpetuated, but this does not provide an entirely accurate reflection of ischemic pathophysiology and imaging insight shows far more than time alone. Maximizing the potential of perfusion imaging will continue to expand the nascent concept that cerebral ischemia may be completely reversible in certain scenarios. Novel modalities provide a fertile ground for discovery of therapeutic targets and the potential to assess effects of promising strategies. Beyond clinical trials, imaging has become a requisite component of the neurological examination enabling tailored stroke therapy with the use of detailed neuroimaging modalities. In this first article on ischemia, the focus is on the most recent imaging advances and exploring aspects of cerebral ischemia where imaging may yield additional therapeutic strategies. A subsequent article will review recent and anticipated imaging advances in hemorrhage. These thematic overviews underscore that imaging will undoubtedly continue to dramatically shape the future of stroke.

Early Predictive Biomarkers for Lesion After Transient Cerebral Ischemia

“…Moreover, the observation of glutamine increase in patients with TIA can help determine which areas had a lack of perfusion. The advantage of MRS compared with routinely used imaging techniques 34 is its capacity to identify recent ischemic events and predict outcome in the first hours after reperfusion, at a time when none of the other techniques detect any abnormality ( Figure 6) and where diagnostic blood biomarkers are less precise. 35 In conclusion, the ability to identify ischemic damage and predict the outcome (neuronal loss or recovery) based on metabolite concentrations between 3 and 8 hours after ischemia opens exciting perspectives for stroke diagnosis and treatment.…”

Intracranial Atherosclerotic Stroke - Hemodynamic Features and Role of MR Angiography

“…8,11 Longstanding hemodynamic compromise which was frequently observed in intracranial atherosclerosis may elicit collateral development and preconditioning to adapt to recurrent ischemia. 12 Thus, it is conceivable that patients with intracranial atherosclerosis may be 'prepared' and 'preconditioned' for the risk of subsequent stroke.…”

Outcome Improvement in Acute Stroke Revascularization Procedures

“…В случае, если внутриартериальные вмешательства проводят в клиниках общего профиля или их выполня-ют хирурги с недостаточным опытом работы, риск раз-вития осложнений повышается. Кроме того, пациенты с выраженным несоответствием зон нарушения диффу-зии и перфузии, по результатам нейровизуализирующих исследований головного мозга, получают больше пользы от проведения вмешательства и являются лучшими кан-дидатами [8]. Учет этих факторов при отборе пациентов может повлиять на улучшение результатов.…”

“…Furthermore, patients with large mismatches between diffusion and perfusion on brain neuroimaging studies are more likely to benefit from the procedures and are better candidates. 8 The introduction of these variables in patient selection may improve results.…”