Clinical diffusion mismatch better discriminates infarct growth than mean transit time-diffusion weighted imaging mismatch in patients with middle cerebral artery-M1 occlusion and limited infarct core

Background and purpose Our purpose was to compare clinical diffusion mismatch (CDM) and mean transit time (MTT)-diffusion mismatch as predictors of infarct growth in patients with proximal middle cerebral artery (MCA) occlusion and small infarct core on presentation. Methods Retrospective analysis of consecutive stroke patients with: (1) MCA-M1 occlusion; (2) MRI performed 10h from symptoms onset; and (3) baseline MRI-diffusion weighted imaging (DWI) volume 25mL. Definitions included: CDM=baseline National Institutes of Health Stroke Scale (NIHSS) score 8 and DWI volume 25mL; MTT-DWI mismatch=visually assessed unthresholded MTT lesion ((MTT-DWI))/DWI) 20% and 10mL larger than the DWI lesion; and significant infarct growth (>20% (5mL) increase in infarct volume on follow-up). Uni-/multivariate analyses were performed to define the predictors of infarct growth. Results 63 stroke patients with MCA-M1 occlusions and MRI within 10h of onset were evaluated. 20 patients were excluded on the basis of DWI volume >25mL leaving 43 patients (mean age 75.8years; median NIHSS=13) in the study cohort. On univariate analysis, larger admission DWI volume (p<0.0001), baseline NIHSS score 8 (p=0.001), lack of IV and/or endovascular treatment (p=0.021), glucose levels >125mg/dL (p=0.024), poor CT angiography collaterals (p=0.046), and lower admission Alberta Stroke Program Early CT score (ASPECTS) (p=0.049) predicted infarct growth. Baseline NIHSS score 8 was the only independent predictor of stroke growth in the multivariate analysis (p=0.001). All patients had MTT-DWI mismatch >20%. There was no significant association between the amount of MTT-DWI mismatch and infarct growth (p=0.33). Conclusions CDM is the most powerful predictor of infarct growth in patients with MCA-M1 occlusion and small infarct core. Most of these patients will have a significant oligemic MTT lesion regardless of admission NIHSS score.