FLAIR can estimate the onset time in acute ischemic stroke patients

Abstract Background and purpose Although thrombolysis can be performed for acute ischemic stroke (AIS) within 6 h of onset, patients with an unknown onset time cannot receive this treatment. The aim of the present study is to investigate a method for determining the onset time of stroke in AIS patients within 24 hours (h) of onset. Methods AIS patients with onset time clearly defined within 24 h were enrolled. All patients were examined using diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR). We investigated the utility of FLAIR in estimating the onset time of stroke. Results We enrolled 333 consecutive patients (median age, 74 years [interquartile range, 63–81]; males, 207 [62%]). Fifty-three patients underwent multiple MRI examinations; thus, a total of 389 MRI studies were analyzed. When the MRI findings were DWI-positive and FLAIR-negative (DWI+/FLAIR−), the interval between onset and imaging time was estimated to be within 3 h with sensitivity of 0.83, specificity of 0.71, positive predictive value (PPV) of 0.64, and negative predictive value (NPV) of 0.87; to be within 4.5 h with sensitivity of 0.74, specificity of 0.85, PPV of 0.87, and NPV of 0.70; and to be within 6 h with sensitivity of 0.69, specificity of 0.91, PPV of 0.94, and NPV of 0.59. When patients with infra-tentorial lesions, lacunar stroke on imaging, and mild neurological deficit were excluded, DWI+/FLAIR− estimated that the onset time was within 3 h with sensitivity of 0.93 and PPV of 0.77; within 4.5 h with sensitivity of 0.77 and PPV of 0.96; and within 6 h with sensitivity of 0.74 and PPV of 1.00. Conclusion FLAIR can estimate the onset time of stroke in AIS within 24 h of onset.