Role of Apparent Diffusion Coefficient Gradient Within Diffusion Lesions in Outcomes of Large Stroke After Thrombectomy

Background and Purpose: The outcome of endovascular treatment in stroke patients with a large ischemic core is not always satisfactory. We evaluated whether the severity of baseline diffusion-weighted imaging abnormalities, as assessed by different apparent diffusion coefficient (ADC) thresholds, correlates with the clinical outcome in these patients after successful endovascular treatment. Methods: In 82 consecutive patients with a large vessel occlusion in the anterior circulation admitted <= 24 hours after onset, a baseline diffusion lesion volume (ADC <= 620x10(-6) mm(2)/s [ADC(620)]) >= 50 mL and successful recanalization by endovascular treatment were retrospectively investigated. Lesion volumes of 3 ADC thresholds (ADC(620), ADC <= 520x10(-6) mm(2)/s [ADC(520)], and ADC <= 540x10(-6) mm(2)/s [ADC(540)]) were measured using an automated Olea software program. The performance of the ADC(520)/ADC(620) and ADC(540)/ADC(620) ratios in predicting the functional outcome was assessed by receiver operating characteristic curve analysis. The ADC ratio with optimal threshold showing better receiver operating characteristic performance was dichotomized at its median value into low versus high subgroup and its association with the outcome subsequently evaluated in a multivariable logistic regression model. Results: The median baseline diffusion lesion volume was 80.8 mL (interquartile range, 64.4-105.4). A good functional outcome (modified Rankin Scale score, <= 2) was achieved in 35 patients (42.7%). The optimal threshold for predicting the functional outcome was identified as ADC(540)/ADC(620) (area under the curve, 0.833) and dichotomized at 0.674. After adjusting for age, baseline National Institutes of Health Stroke Scale score, intravenous tissue-type plasminogen activator, baseline diffusion lesion volume, and onset-to-recanalization time, a low ADC(540)/ADC(620) was independently associated with a good functional outcome (adjusted odds ratio, 10.72 [95% CI, 3.06-37.50]; P<0.001). Conclusions: A low ADC(540)/ADC(620), which may reflect less severe ischemic stress inside a diffusion lesion, may help to identify patients who would benefit from endovascular treatment despite having a large ischemic core.