The Role of the Signal Intensity Ratio on Fluid-Attenuated Inversion Recovery in Stroke Patients Achieving Successful Recanalization with Endovascular Treatment

Abstract

Background: This study aimed to investigate whether fluid-attenuated inversion recovery (FLAIR) imaging hyperintensity can be used as a surrogate marker for the severity of ischemic insult and predict lesion growth. Methods: Based on a prospective stroke registry database, we identified patients with ischemic stroke who were treated with endovascular treatment (EVT) within 8 hours of onset and achieved successful recanalization (modified thrombolysis in cerebral infarction >= 2B). FLAIR hyperintensity was measured using the signal intensity ratio (SIR), defined as the mean SIR of diffusion-restricted lesions to the corresponding areas in the contralateral hemisphere. Lesion growth was defined as the ratio of final infarct volume on follow-up FLAIR to initial infarct volume on diffusion-weighted imaging. Results: For 69 patients meeting the eligibility criteria, the median FLAIR SIR was 1.17 (interquartile range, 1.08-1.23) and the median lesion growth ratio was 1.70 (interquartile range, 1.35-2.79) (Pearson's r = -.146, P = .231). In multiple linear regression models, the FLAIR SIR was not significantly correlated with the lesion growth ratio. Interestingly, the time interval from initial magnetic resonance imaging (MRI) to successful recanalization was independently correlated with the lesion growth ratio (beta=.072, P<.001). With respect to clinical outcomes, the FLAIR SIR was not associated with either discharge modified Rankin scale score <= 2 (beta = -3.41, P=.30) or symptomatic hemorrhagic transformation (beta = 2.75; P = .63). Conclusions: Contrary to our hypothesis, FLAIR hyperintensity on initial MRI before EVT was not associated with lesion growth in patients who were recanalized successfully with EVT. Instead, our results suggest that time interval from MRI acquisition to recanalization is an independent predictor of lesion growth.