How Sustained Is 24-Hour Diffusion-Weighted Imaging Lesion Reversal? Serial Magnetic Resonance Imaging in a Patient Cohort Thrombolyzed

A ll current MR-based approaches in candidates for reper-fusion therapy depend on diffusion-weighted imaging (DWI) for an accurate assessment of infarct core. DWI is necessary not only to map the perfusion weighted imaging– DWI mismatch but also in relation to lesion volume cutoffs above which thrombolysis may not have clinical benefit or be even harmful. However, the widely prevalent model that at early time points, the DWI lesion exclusively represents the infarct core has been a matter of controversy. Both early animal research 1–3 and recent clinical studies 4–8 have reported that DWI lesions can reverse either spontaneously or after recanalization, suggesting that they contain not only core but also some pen-umbral tissue. Thus, DWI lesion reversal has been reported in one third of patients after recanalization therapy 9 and in up to one half after intravenous thrombolysis. 6 In the latter population , DWI lesion reversal at 24 hours was associated with early Background and Purpose—Here, we assessed how sustained is reversal of the acute diffusion lesion (RAD) observed 24 hours after intravenous thrombolysis, and the relationships between RAD fate and early neurological improvement. Methods—We analyzed 155 consecutive patients thrombolyzed intravenously 152 minutes (median) after stroke onset and who underwent 3 MR sessions: 1 before and 2 after treatment (median times from onset, 25.6 and 54.3 hours, respectively). Using voxel-based analysis of diffusion-weighted imaging (DWI) 1 , DWI 2 , and DWI 3 lesions on coregistered image data sets, we assessed the outcome of RAD voxels (hyperintense on DWI 1 but not on DWI 2) as transient or sustained on DWI 3 , and their relationships with early neurological improvement, defined as ΔNational Institutes of Health Stroke Scale ≥8 or National Institutes of Health Stroke Scale ≤1 at 24 hours. T max and apparent diffusion coefficient values were compared between sustained and transient RAD voxels. Results—The median (interquartile range) baseline National Institutes of Health Stroke Scale and DWI 1 lesion volume were 11 (7–18) mL and 15.6 (6.0–50.9) mL, respectively. The median (interquartile range) RAD volume on DWI 2 was 2.8 (1.1–6.6) mL, of which 70% was sustained on DWI 3. Sixteen (10.3%) patients had sustained RAD ≥10 mL. As compared with transient RAD voxels, sustained RAD voxels had nonsignificantly higher baseline apparent diffusion coefficient values (median [interquartile range], 793 [717–887] versus 777 [705–869]×10