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DWI-FLAIR mismatch identified acute ischemic lesion within 4.5 hours of symptom onset
Thomalla G. Lancet Neurol. 2011;doi:10.1016/S1474-4422(11)70192-2.
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Use of diffusion-weighted MRI and fluid-attenuated inversion recovery MRI mismatch may be used as a surrogate marker to identify patients with acute ischemic stroke who are eligible for intravenous thrombolysis, researchers reported.
Researchers analyzed clinical and MRI data from patients with acute ischemic stroke who had undergone diffusion-weighted (DWI) MRI and fluid-attenuated inversion recovery (FLAIR) MRI within 12 hours of observed symptom onset. Acute ischemic lesions were judged by visibility on DWI and FLAIR imaging, which diagnosed DWI-FLAIR mismatch. Predictive values of DWI-FLAIR were calculated for identification of patients with symptom onset, and potential confounding covariates were identified through multivariate regression analysis, according to the study.
Of 543 patients studied, acute ischemic lesions were identified on DWI in 95% and on FLAIR in 50%. The researchers noted 62% sensitivity, 78% specificity, 83% positive predictive value and 54% negative predictive value of DWI-FLAIR mismatch identification of patients within 4.5 hours of symptom onset, according to study results.
The researchers said interobserver agreement for acute ischemic lesion visibility was moderate on FLAIR imaging. Additionally, independent predictors of lesion visibility on FLAIR imaging included a longer time to MRI (P<.0001), lower age (P=.0009) and larger DWI lesion volume (P=.0226), multivariate regression analysis revealed.
“This study sets the stage for optimization and validation for the FLAIR-DWI mismatch biomarker,” Michael D. Hill, MD, and Richard Frayne, MD, of the Hotchkiss Brain Institute in Calgary, Canada, wrote in an accompanying editorial. “Validation would allow this biomarker to be used as a participant selection method for randomized trials of thrombolytic stroke therapy in patients with stroke on awakening or with unwitnessed stroke onset. Such trials are on the drawing board and it will be these kinds of imaging biomarkers — which are simple, practical, and easily implementable at many sites — that will allow relevant candidate to be selected for enrolment in these trials.”
Disclosure: Dr. Thomalla has received a research grant from the Else Kröner-Fresenius-Stiftung.
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