Brain edema predicts outcome after nonlacunar ischemic stroke

Abstract

Background and purpose: In malignant infarction, brain edema leads to secondary neurological deterioration and poor outcome. We sought to determine whether swelling is associated with outcome in smaller volume strokes.

Methods: Two research cohorts of acute stroke subjects with serial brain MRI were analyzed. The categorical presence of swelling and infarct growth was assessed on diffusion-weighted imaging (DWI) by comparing baseline and follow-up scans. The increase in stroke volume (ΔDWI) was then subdivided into swelling and infarct growth volumes using region-of-interest analysis. The relationship of these imaging markers with outcome was evaluated in univariable and multivariable regression.

Results: The presence of swelling independently predicted worse outcome after adjustment for age, National Institutes of Health Stroke Scale, admission glucose, and baseline DWI volume (odds ratio, 4.55; 95% confidence interval, 1.21-18.9; P<0.02). Volumetric analysis confirmed that ΔDWI was associated with outcome (odds ratio, 4.29; 95% confidence interval, 2.00-11.5; P<0.001). After partitioning ΔDWI into swelling and infarct growth volumetrically, swelling remained an independent predictor of poor outcome (odds ratio, 1.09; 95% confidence interval, 1.03-1.17; P<0.005). Larger infarct growth was also associated with poor outcome (odds ratio, 7.05; 95% confidence interval, 1.04-143; P<0.045), although small infarct growth was not. The severity of cytotoxic injury measured on apparent diffusion coefficient maps was associated with swelling, whereas the perfusion deficit volume was associated with infarct growth.

Conclusions: Swelling and infarct growth each contribute to total stroke lesion growth in the days after stroke. Swelling is an independent predictor of poor outcome, with a brain swelling volume of ≥11 mL identified as the threshold with greatest sensitivity and specificity for predicting poor outcome.

Keywords: brain edema; magnetic resonance imaging; stroke; swelling.

Figure 1. Examples of swelling, infarct growth, and both

Baseline DWI was compared to the co-registered follow-up DWI to assess the presence of swelling or infarct growth. (A) A patient who developed swelling between baseline and follow-up scan, demonstrating ventricular effacement and expansion of the caudate head (solid arrows) and loss of sulci (dotted arrows). (B) An example of both swelling (solid arrows) and infarct growth (dashed arrows). (C) An example of infarct growth (dashed arrows).The right hand most images in each panel demonstrate the volumes attributed to either swelling or infarct growth. BL=baseline; FU=follow-up; ROI=region of interest on the follow-up scan.

Figure 2. Distribution of 90-day modified Rankin Scale scores for subjects with and without swelling or infarct growth

The distribution of outcomes for swelling and infarct growth are shown, with the right hand key representing each category of mRS as labeled. The height of each bar represents the percentage of the cohort with each score.

Figure 3. Greater swelling is associated with poor neurological outcome

(A) The volume of swelling in subjects with mRS of 3-6 was higher than those with a 90 day mRS of 0-2 (p < 0.001). (B) Receiver operating characteristic (ROC) curve analysis shows that swelling of 11mL predicts poor outcome with a sensitivity of 77% and a specificity of 75%, identified by the arrow. The area under the curve was 0.798.