Quantitative Signal Intensity in Fluid-Attenuated Inversion Recovery and Treatment Effect in the WAKE-UP Trial

Background and Purpose—

Relative signal intensity of acute ischemic stroke lesions in fluid-attenuated inversion recovery (fluid-attenuated inversion recovery relative signal intensity [FLAIR-rSI]) magnetic resonance imaging is associated with time elapsed since stroke onset with higher intensities signifying longer time intervals. In the randomized controlled WAKE-UP trial (Efficacy and Safety of MRI-Based Thrombolysis in Wake-Up Stroke Trial), intravenous alteplase was effective in patients with unknown onset stroke selected by visual assessment of diffusion weighted imaging fluid-attenuated inversion recovery mismatch, that is, in those with no marked fluid-attenuated inversion recovery hyperintensity in the region of the acute diffusion weighted imaging lesion. In this post hoc analysis, we investigated whether quantitatively measured FLAIR-rSI modifies treatment effect of intravenous alteplase.

Methods—

FLAIR-rSI of stroke lesions was measured relative to signal intensity in a mirrored region in the contralesional hemisphere. The relationship between FLAIR-rSI and treatment effect on functional outcome assessed by the modified Rankin Scale (mRS) after 90 days was analyzed by binary logistic regression using different end points, that is, favorable outcome defined as mRS score of 0 to 1, independent outcome defined as mRS score of 0 to 2, ordinal analysis of mRS scores (shift analysis). All models were adjusted for National Institutes of Health Stroke Scale at symptom onset and stroke lesion volume.

Results—

FLAIR-rSI was successfully quantified in stroke lesions in 433 patients (86% of 503 patients included in WAKE-UP). Mean FLAIR-rSI was 1.06 (SD, 0.09). Interaction of FLAIR-rSI and treatment effect was not significant for mRS score of 0 to 1 ( P =0.169) and shift analysis ( P =0.086) but reached significance for mRS score of 0 to 2 ( P =0.004). We observed a smooth continuing trend of decreasing treatment effects in relation to clinical end points with increasing FLAIR-rSI.

Conclusions—

In patients in whom no marked parenchymal fluid-attenuated inversion recovery hyperintensity was detected by visual judgement in the WAKE-UP trial, higher FLAIR-rSI of diffusion weighted imaging lesions was associated with decreased treatment effects of intravenous thrombolysis. This parallels the known association of treatment effect and elapsing time of stroke onset.

Association of Reperfusion With Brain Edema in Patients With Acute Ischemic Stroke: A Secondary Analysis of the MR CLEAN Trial

Importance

It is uncertain whether therapeutic reperfusion with endovascular treatment yields more or less brain edema.

Objective

To elucidate the association between reperfusion and brain edema. The secondary objectives were to evaluate whether brain edema could partially be responsible for worse outcomes in patients with later reperfusion or lower Alberta Stroke Program Early Computed Tomography Score.

Design, Setting, and Participants

This was a post hoc analysis of the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN), which was a prospective, randomized, multicenter clinical trial of endovascular treatment compared with conventional care of patients with acute anterior circulation ischemic stroke. Of 502 patients enrolled from December 2010 to June 2014, 2 patients declined to participate. Additionally, exclusion criteria were absence of follow-up imaging or presence of parenchymal hematoma, resulting in 462 patients included in this study. Brain edema was assessed retrospectively, from December 10, 2016, to July 24, 2017, by measuring midline shift (MLS) in all available follow-up scans. Observers were blinded to clinical data.

Main Outcomes and Measures

Midline shift was assessed as present or absent and as a continuous variable. Reperfusion status was assessed by the modified thrombolysis in cerebral infarction score in the endovascular treatment arm. The modified arterial occlusive lesion score was used to evaluate the recanalization status in both arms. The modified Rankin scale score at 90 days was used for functional outcome.

Results

Of 462 patients, the mean (SD) age was 65 (11) years, and 41.8% (n = 193) were women. Successful reperfusion and recanalization were associated with a reduced likelihood of having MLS (adjusted common odds ratio, 0.25; 95% CI, 0.12-0.53; P < .001 and adjusted common odds ratio, 0.34; 95% CI, 0.21-0.55; P < .001, respectively). Midline shift was partially responsible for worse modified Rankin scale scores in patients without reperfusion or recanalization (MLS changed the logistic regression coefficients by 30.3% and 12.6%, respectively). In patients with delayed reperfusion or lower Alberta Stroke Program Early Computed Tomography Score, MLS mediated part of the worse modified Rankin scale scores, corresponding to a change in the regression coefficient of 33.3% and 64.2%, respectively.

Conclusions and Relevance

Successful reperfusion was associated with reduced MLS. This study identifies an additional benefit of reperfusion in relation to edema, as well as rescuing ischemic brain tissue at risk for infarction.

Trial Registration

Netherlands Trial Registry number: NTR1804 and Current Controlled Trials number: ISRCTN10888758.

Abstract WP5: Reperfusion Reduces Brain Edema in Patients With Acute Ischemic Stroke. A MR CLEAN Substudy

Introduction: The main objective of this study was to elucidate the relation between reperfusion and brain edema. The secondary objective was to evaluate if brain edema partially mediated worse outcome in patients without reperfusion, or in patients with delayed reperfusion or a lower ASPECTS.

Methods: MR CLEAN was a prospective, randomized, multicenter clinical trial of endovascular treatment (EVT) compared to conventional care. In this exploratory post hoc study, 462 of 500 patients were included. Brain edema was assessed by midline shift (MLS) measured on follow-up CT scans. Reperfusion status was assessed by the modified thrombolysis in cerebral infarction (mTICI) score in the EVT arm. The modified Arterial Occlusive Lesion (mAOL) score was used to evaluate the recanalization status in both arms. The associations between MLS and modified Rankin Scale (mRS), and MLS with reperfusion or recanalization were performed in univariable and multivariable analyses. Mediation analyses were performed to determine whether MLS was partially responsible for worse functional outcome in the groups without reperfusion or recanalization, and in the groups with delayed reperfusion or lower ASPECTS.

Results: Reperfusion and recanalization were associated with reduced likelihood of having MLS (acOR 0.26, 95%CI 0.13-0.51, p < 0.001; acOR 0.38, 95%CI 0.24-0.60, p < 0.001 respectively). Accordingly, the presence of MLS was associated with an increased risk of worse 90-day outcome (acOR 3.89, CI 2.71-5.61, p < 0.001). In mediation analysis, MLS was partially responsible for worse mRS scores in patients without reperfusion or recanalization, and in those with delayed reperfusion or lower ASPECTS (MLS changed the logistic regression coefficients by 30.3%, 12.6%, 33.3%, and 64.2%, respectively).

Conclusion: Successful reperfusion or recanalization reduces brain edema, reflected by MLS. The presence of MLS mediated part of the worse functional outcomes in patients without reperfusion or in those patients with delayed reperfusion or a lower ASPECTS. This study confirms a pleiotropic benefit of reperfusion that extends beyond the concept of rescuing ischemic brain tissue at risk for infarction.