This was a prospective case-control study. Consecutive acute ischemic stroke patients were prospectively recruited. Inclusion criteria were stroke onset within 48 h, MRI brain with DWI was available, non-lacunar anterior circulation infarction on MRI, no significant pre-stroke disability (Modified Rankin Scale score < 2) and age > 18 years. Patients were excluded if they had significant concurrent electrolyte imbalance or uncontrolled general metabolic derangements.
MRI
Brain MRI was acquired using a 1.5T machine (Signa Prospeed, GE, USA) including Fast Spin Echo T1W (TE/TR 9/520 ms), T2W (TE/TR 105/5000 ms), axial fluid-attenuated inversion recovery (FLAIR) (TE/TR 140/8000 ms, inversion time 2 s), axial single-shot multi-slice diffusion-weighted echo-planar imaging pulse sequence (DWI-EPI) (b value = 1000, TE/TR 112/6300 ms) and EPI gradient echo T2* (TE/TR 15/540 ms), and time-of-flight MRA (TE/TR 6.9/36 ms).
DWI homogeneity
Visual assessment of DWI images was done by two examiners to classify lesions into homogenous and non-homogenous (heterogeneous). A DWI lesion was considered homogenous if there was (1) no clearly discernable or very little differences in signal intensity in different parts of the lesion (featureless uniform hyperintensity); (2) loss of grey-white matter differentiation if lesion involved the cortex; (3) loss of structural details of the parenchyma within the lesion; and (4) no clear hemorrhagic transformation within the lesion (Fig. 1). Lesions were considered non-homogenous (heterogeneous) if they did not fulfil these criteria (i.e., showed variable degrees of hyperintensity in various parts of the lesion). Using these simple criteria, there was excellent inter-rater or intra-rater variability in the study sample (k = 0.94, p < 0.01; k = 0.98, p < 0.01; respectively).
Lesion sizes were divided based on measuring of maximum diameter on axial sections by trained neurologists (RRM, HHS) into small (2–3 cm), medium (3–5 cm), and large (> 5 cm) infarctions.
Outcome measures
NIHSS was assessed at baseline, at 1 week (or discharge from hospital) and at 1 month after onset. Modified Rankin Scale (mRS) was assessed at 3 months.
Informed consent was obtained from all subjects or their next of kin. The study was approved by the Ain Shams University Local Research Ethics Committee.
Statistical analysis
Comparisons were made between groups (homogeneous vs. non-homogenous DWI lesion) in mRS at 3 months using the Mann-Whitney U test (median and interquartile range [IQR]) and in NIHSS at baseline, 1 week and at 1 month using repeated-measures ANOVA. Comparison of lesion sizes between groups was done using chi-squared test. The analysis was done on SPSS ver. 20 (IBM SPSS, NY, USA). p < 0.05 was considered significant.