CT/NIHSS Mismatch for Detection of Salvageable Brain in Acute Stroke Triage Beyond the 3-Hour Time Window

Abstract

See related article, pages 2079–2084. Although the only FDA-approved medical therapy for acute stroke to date remains intravenous tissue plasminogen activator administered within 3 hours of onset, there is increasing evidence that identification of potentially salvageable brain using advanced imaging may facilitate the selection of patients for safe and effective intravenous thrombolysis up to 9 hours postictus.1–5 Specifically, the mismatch between infarct core (brain likely to be irreversibly infarcted despite treatment) and ischemic penumbra (hypoperfused brain at risk for infarction in the absence of reperfusion) may identify patients with both a low hemorrhagic risk (small core) and a high likelihood of treatment benefit (large penumbra). In clinical practice, core can be operationally defined using either MR diffusion-weighted imaging (DWI) or CT cerebral blood volume imaging, and penumbra with either MR or CT perfusion-weighted imaging (PWI); conventional unenhanced CT provides a less sensitive measure of core.6–8 Because many sites do not currently have access to advanced CT and MR modalities, however, and not all patients are candidates for such scanning even when it is available, there has been interest in using the mismatch between CT hypodensity and clinical NIHSS as a surrogate for radiographic core/penumbra mismatch. In this issue of Stroke , Messe et al9 report that, for a community-based cohort of acute stroke patients, CT/NIHSS mismatch “could not be validated as a means to identify ischemic penumbra as defined by MRI diffusion-perfusion mismatch.” MRI …