Abstract
Magnetic resonance imaging has tremendous potential to illuminate ischemic stroke pathophysiology and guide rational treatment decisions. Clinical applications to date have been largely limited to trials. However, recent analyses of the major clinical studies have led to refinements in selection criteria and improved understanding of the potential implications for the risk vs. benefit of thrombolytic therapy. In parallel, preclinical studies have provided complementary information on the evolution of stroke that is difficult to obtain in humans due to the requirement for continuous or repeated imaging and pathological verification. We review the clinical and preclinical advances that have led to perfusion-diffusion mismatch being applied in phase 3 randomized trials and, potentially, future routine clinical practice.
Highlights
We review the clinical and preclinical advances that have led to perfusion–diffusion mismatch being applied in phase 3 randomized trials and, potentially, future routine clinical practice
Studies using Positron emission tomography (PET) in a limited number of human patients with a variable degree of stroke acuity have suggested that similar relative thresholds, corresponding to a penumbra range of cerebral blood flow (CBF) ∼17–22 ml/100 g/min, apply in man [33,34,35]
Type and depth of anesthesia can influence the temporal change in the apparent diffusion coefficient (ADC) lesion and perfusion deficit and the assessment of penumbra from diffusion-weighted imaging (DWI)/Perfusion imaging (PI) or ADC/PI mismatch
Summary
Patients with large baseline diffusion-weighted imaging (DWI) lesions very rarely achieve a favorable clinical outcome, regardless of the success of reperfusion attempts. These patients may be at greater risk of harm from reperfusion – the concept of ‘malignant’ or ‘futile’ profile [6]. Studies using PET in a limited number of human patients with a variable degree of stroke acuity have suggested that similar relative thresholds, corresponding to a penumbra range of cerebral blood flow (CBF) ∼17–22 ml/100 g/min, apply in man [33,34,35]. A Tmax >6 s perfusion threshold was used in DEFUSE 2 [8], which confirmed the benefits of reperfusion in patients with mismatch beyond 4·5 h and is employed in the ongoing EXTEND trial [9]
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