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Reperfusion therapy is the only proven treatment for acute ischemic stroke.1 ,2 For proximal arterial occlusions, intra-arterial treatment (IAT) yields substantially higher rates of early revascularization than FDA-approved treatment with intravenous tissue plasminogen activator (tPA).3 However, recent randomized controlled trials (RCTs) show no added clinical benefit of IAT compared with standard medical management.4–6 Although there are clear limitations to these trials,7 a major lesson is that the signal of benefit favoring IAT is much smaller than expected. In this context, improving patient selection for IAT remains essential, with neuroimaging playing a central role. This article begins with a pathophysiologic argument for the importance of imaging, discusses the available neuroimaging tools and their reliability and reviews the evidence supporting the use of imaging to predict the response to IAT.
The ‘time is brain’ approach to patient selection: can neuroimaging provide added value?
Current guidelines recommend a time window of 6 h for intra-arterial thrombolysis.8 Mechanical therapies are cleared for use up to 8 h. Although the time window for IAT efficacy remains unclear,9 treatment efficacy erodes with time,10 placing a clear emphasis on rapid treatment delivery. However, this has come at the expense of potentially valuable neuroimaging as well as a rigorous approach to imaging interpretation. In both the SYNTHESIS Expansion and Interventional Management of Stroke (IMS) III trials (table 1), only a non-contrast CT (NCCT) scan was required prior to enrollment.5 ,6 The primary imaging exclusion criterion for the SYNTHESIS Expansion trial (in addition to hemorrhage) was the presence of well-established infarction (as a marker of potentially longer stroke duration). For IMS III, it was the presence of clear hypodensity involving more than one-third of the middle cerebral artery (MCA) territory. As will be discussed, these findings are of limited value in excluding patients who are unlikely to respond to treatment.
The major limitation of …
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