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

Abstract

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.

Introduction

The first aim of acute ischemic stroke therapy is to prevent the ischemic penumbra from proceeding toward infarction in order to improve the neurological and functional outcomes [1], [2]. Diffusion- (DWI) and perfusion-weighted imaging (PWI) may provide a simple and feasible means of identifying ischemic tissue at risk of infarction. A region with a perfusion but no diffusion abnormality is referred to be a perfusion–diffusion mismatch. Such regions are thought to represent the ischemic penumbra and be the strongest predictors of ischemic lesion growth, and are regarded as ‘tissue-at-risk’ [3], [4]. Over 75% of patients suffering an acute ischemic stroke within 6 h of stroke onset have been found to have perfusion lesions larger than the corresponding diffusion lesions, which is the major target of reperfusion or neuroprotective therapy [5], [6], [7], [8].

For a given amount of initial perfusion abnormality, ischemic lesion growth within a perfusion–diffusion mismatch can vary depending upon the degree of vessel occlusion, collateral supply or hypoperfusion [9], [10]. Indeed, the underlying pathophysiology of vessel occlusion is heterogeneous (i.e., embolic or thrombotic occlusion), and the type of occlusion may influence the temporal evolution of an ischemic lesion within a perfusion abnormality. However, the differential patterns of clinical and radiological evolution according to stroke subtypes remain relatively unknown.

The present study investigated acute middle cerebral artery (MCA) infarctions with a perfusion–diffusion mismatch to determine whether atherosclerotic and cardioembolic MCA occlusions differed in terms of the evolution of clinico-radiological patterns. The study also compared the atherosclerotic and cardioembolic groups in terms of the correlation between infarct volume and clinical severity.