Introduction and Hypothesis: Several studies found that critical infarct volumes <30 mL best predict good outcome after acute ischemic stroke. This is an important issue in light of increasing use of advanced imaging methodologies to select patients based on imaging rather than purely time-based criteria. The burden of pre-existing white matter disease (WMD) has been shown to impact infarct extent, functional deficit severity, and final outcome. We hypothesized that the threshold best predicting outcome is significantly modulated by the degree of pre-existing WMD burden.
Methods: We quantified infarct volumes on diffusion-weighted imaging using manual planimetry in 371 consecutive patients with supratentorial, anterior circulation ischemic strokes evaluated between January 2014 and December 2014. WMD was graded according to the Fazekas score and dichotomized to mild (Fazekas 0-2) vs. severe (Fazekas 3-6). Receiver operator characteristics curves were calculated to determine the lesion-threshold (mL) best predicting an excellent, good, and favorable outcome at 90-days as defined as modified Rankin scale score of 0-1, 0-2, and 0-3, respectively.
Results:Figure 1. In the entire cohort, the ischemic lesion thresholds best predicting outcome were similar across 90-day outcome categories (∼25-30 mL; Figure 1 A&B) and consistent with thresholds defined by prior studies. However, patients with mild WMD tolerated 51% and 72% greater ischemic infarct volumes than patients with severe WMD to achieve good and favorable outcomes, respectively.
Conclusions: “Standard” lesion thresholds may be too restrictive in predicting a good outcome in patients with mild WMD. Adjusting for markers of brain health such as WMD burden may improve on lesion threshold definition to predict outcome.