Stroke

Defining MRI tissue signatures predicting favorable response to intravenous tissue plasminogen activator may allow for identifying patients amenable to treatment beyond the established time window. Krützelmann and colleagues analyzed data from 174 patients with acute ischemic stroke from a prospective multicenter observational study receiving intravenous tissue plasminogen activator treatment within 6 hours from symptom onset based on time window (0 to 3 hours) or MRI criteria (3 to 6 hours). Predictors of favorable outcome (receiver operating characteristic curve analysis-defined threshold) were a younger age ( 63 years), lower admission National Institutes of Health Stroke Scale ( 13), and smaller diffusion-weighted imaging lesion volume ( 16 mL). The authors found that there was no significant effect of onset to treatment time ( 3 hours versus 3 to 6 hours) following multivariate regression analysis. Conversely, mortality was predicted by age only. In line with prior studies, pretreatment diffusion-weighted imaging lesion volume appears associated with outcome; however, as the author’s caution, the defined diffusion-weighted imaging threshold should not be used for clinical decision-making for various reasons. For example, site and extent of arterial occlusion and recanalization rates are unknown. In addition, collateral status, comorbidities, and lesion location were not considered. Lastly, consistent with prior important large clinical trials, the author’s dichotomized outcome into favorable (modified Rankin Scale 1) versus unfavorable (modified Rankin Scale 2), yet, some may feel that categorizing modified Rankin Scale 2 as “unfavorable” might be too stringent. Additional valuable information might be provided by analysis modalities such as the Cochran-Mantel-Haenszel shift test independent on prespecified binary outcomes. See p 1251.