Neuroimaging (MRI) of acute stroke: Present role in clinical management and research

Over the past two decades developments in neuro-imaging, especially magnetic resonance imaging (MRI), have enabled enormous changes to be made in our knowledge and understanding of acute stroke, and this knowledge is now being applied to stroke management and research. Emergent MRI is in clinical use as the first-line investigation for acute stroke in a number of clinical centers around the world. A useful clinical development has been the report of a three-item scale for the early prediction of stroke recovery (as early as 3 to 6 hours after onset), using a combination of MRI diffusion-weighted imaging and clinical parameters. Rapid vascular imaging from the aortic arch to the circle of Willis using contrast-enhanced MR angiography (CE-MRA) is being assessed: it could complement acute stroke MRI protocols, being of particular value for emergent decisions regarding acute stroke intervention (intravenous and intra-arterial thrombolysis), urgent surgical intervention and secondary stroke prevention. CE-MRA could also permit the detection of some vascular causes of stroke that previously went unrecognized. In new research applications, MRI perfusion and diffusion patterns are being used as selection criteria in acute stroke drug trials. By selecting patients with tissue still potentially salvageable by reperfusion, the time window for thrombolytic treatment may be extended from the conventional 3 hours up to 6 or even 24 hours after symptom onset. Real-time high resolution MRI is also being combined with peripheral blood markers in gene and protein expression profiling studies, along with markers of inflammation, to study patterns of stroke risk, evolution and recovery.