Jay Shah, MD
Legrand L, Tisserand M, Turc G, Edjlali M, Calvet D, Trystram D, et al. Fluid-Attenuated Inversion Recovery Vascular Hyperintensities–Diffusion-Weighted Imaging Mismatch Identifies Acute Stroke Patients Most Likely to Benefit From Recanalization. Stroke. 2016
Perfusion-Diffusion mismatch on MRI has been proposed to select ischemic stroke patients for revascularization therapy. However, this strategy is time consuming and requires gadolinium. The authors previously have reported using mismatch between Fluid-attenuated inversion recovery (FLAIR) vascular hyperintensities (FVH) and diffusion for penumbral evaluation. FVH represent slow retrograde flow in leptomeningeal collaterals and are thought to represent impaired but viable tissue. The authors hypothesize that recanalization after IV-tPA would have better outcomes within FVH-DWI mismatch patients than non-mismatch patients. 
This study was a retrospective analysis of a prospective registry of patients treated exclusively with standard IV-tPA dosing for acute stroke between 2004-14. Other inclusion criteria included proximal M1 occlusion, pre-treatment and 24-hour follow-up MRI, and 3 month modified rankin scale (mRS) score. FVH-DWI mismatch was considered present when FVH extended beyond boundaries of the cortical DWI lesion. In total, 164 patients were included in the analysis. 121 patients had FVH-DWI mismatch. Complete recanalization occurred in 50 patients. Association between recanalization and favorable outcome was significant in patients with FVH-DWI mismatch (OR= 16.2).
This study shows that DWI and FLAIR images can identify patients who are more likely to benefit from recanalization and the authors propose that this modality can be used as a surrogate to perfusion imaging. However, it is clearly understood that clinical outcomes in acute ischemic stroke is strongly associated with recanalization of the occluded artery. Non-mismatch patients also demonstrated benefit, albeit to a lesser degree and therefore revascularization should not be withheld for a perceived lack of benefit. Furthermore, all patients within this study had M1 occlusion but did not undergo endovascular intervention which is now established as the standard of care. For such patients, if recanalization can be achieved according to guideline recommendations, there should not be a need for further penumbral evaluation. However, in patients with a prolonged presentation or an unknown time of onset, assessment of mismatch could provide utility in selecting appropriate patients. Further studies should focus on this patient population.
