About 30% of wake-up stroke patients may be candidate for the tPA therapy using Negative-FLAIR as a "tissue clock"

Background and purpose: Recent studies using magnetic resonance imaging (MRI) have reported that wake-up stroke (WUS) patients may be able to be treated using tissue-plasminogen activator (tPA) when showing no ischemia on fluid-attenuated inversion recovery (Negative-FLAIR). We investigated the frequency of WUS and calculated what percentage of WUS patients with Negative-FLAIR meets most of the conventional tPA criteria. We did not include a time parameter in this study.

Methods: Consecutive patients with acute stroke affecting the anterior circulation who presented within 12h of onset were enrolled. All patients were examined using diffusion-weighted imaging (DWI) and FLAIR. As large infarctions are excluded from tPA therapy, an Alberta Stroke Program Early Computed Tomography Score (DWI-ASPECTS) of ≤3 was used as the upper limit for exclusion.

Results: A total of 816 consecutive patients were included in the study and were separated into two groups; 163 (20%) WUS patients as the WUS group, and 653 (80%) non-WUS patients as the non-WUS group. The median National Institutes of Health Stroke Scale (NIHSS) score on admission was 7 (interquartile range, 3-17) in the WUS group and 8 (3-16) in the non-WUS group (p=0.313). MRI study revealed Negative-FLAIR in 67 (41%) of 163 patients in the WUS group. Of the 67 patients with Negative-FLAIR, 19 patients were excluded from tPA therapy. Therefore, 48 (29%) of the 163 wake-up stroke patients met the tPA criteria.

Conclusions: About 30% of WUS patients may be candidates for tPA therapy based upon Negative-FLAIR findings.