Differential patterns of evolution in acute middle cerebral artery infarction with perfusion-diffusion mismatch: Atherosclerotic vs. cardioembolic occlusion

Background: An acute perfusion-diffusion mismatch is known to be the strongest predictor of infarct growth. However, the differential patterns of clinical and radiological evolution according to stroke mechanism are unknown. Methods: The study retrospectively reviewed consecutive patients who had 1) acute middle cerebral artery (MCA) territory infarction, 2) diffusion- and perfusion-weighted imaging (DWI and PWI) and MR angiography within 24 h of onset, and follow-up DWI 5 days later, 3) stenosis (≥ 50%) or occlusion of MCA on baseline imaging, 4) a baseline PWI-DWI mismatch > 20%, and 5) either atherosclerotic MCA disease (MCAD) or cardioembolism (CE). National Institutes of Health Stroke Scale (NIHSS) scores and infarct volume at baseline and 5 days were obtained. Results: Of 90 patients, 52 had MCAD and 38 had CE. At baseline, CE group had more severe stroke (median NIHSS, 9 vs. 5; p = 0.001) and larger infarct volume (median 8.32 cc vs. 3.0 cc; p = 0.034) than MCAD group. During the 1-week period, CE group had larger infarct volume growth (median 12.85 cc vs. 3.02 cc; p = 0.004) than MCAD group, although clinical improvement based on NIHSS (baseline minus 5-day) tended to be higher for CE than MCAD group (median 3 vs. 1; p = 0.08). The correlation between infarct volume and NIHSS score was stronger in CE (r = 0.841) compared to MCAD (r = 0.582) group at 5-day. Conclusions: Substantial differences in the clinico-radiological evolution of acute ischemic stroke exist according to stroke mechanism. These data emphasize the importance of the stroke mechanism in the design of MRI-based acute stroke trials.