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Advanced MRI to Predict Thrombolysis Outcomes

Advanced MRI is an important predictor of outcomes of thrombolytic treatment given in a 3- to 6-hour window.

Clinicians and researchers have long sought ways to determine whether acute-stroke patients have viable but ischemic brain tissue ("penumbra") that could be saved by reperfusion. Unlike the plain CT scan, clinical examination and advanced MRI and CT protocols can allow clinicians to identify the presence and location of arterial occlusions and the extent of brain infarction and hypoperfusion. To examine whether such techniques can identify patients more likely to benefit from reperfusion, the Diffusion and Perfusion Imaging Evaluation For Understanding Stroke Evolution (DEFUSE) investigators in Europe and North America enrolled 74 consecutive patients with acute ischemic stroke, evaluated and treated in a 3- to 6-hour window after symptom onset. All had diffusion- and perfusion-weighted MRI (DWI and PWI) and magnetic resonance angiography (MRA) immediately before, 3 to 6 hours after IV t-PA infusion, and at 30 days; they had clinical follow-up at 30 and 90 days.

In 46 patients (68% of those with interpretable scans), intracranial occlusions were identified on MRA. Among these patients, those with successful recanalization had better outcomes than those with no recanalization. Early reperfusion led to more favorable clinical outcomes among the 37 patients (54%) with diffusion/perfusion mismatch than in those without mismatch. The 19 patients with small lesions did well. Patients with large DWI and/or PWI lesions (a finding the authors dubbed "malignant pattern") fared poorly: Five of six had brain hemorrhages, and three died.

Comment: DEFUSE shows the effectiveness of using advanced MRI protocols to predict outcomes of thrombolysis. Outcomes clearly depend on whether or not a brain-supplying artery is occluded, if and when it reopens, and how much brain tissue is already infarcted.

No one doubts the utility of modern brain-imaging protocols. These can be performed safely and quickly in most academic medical centers and are helpful in prognosticating and in determining the risks and benefits of potential acute and chronic treatments. All agree that the sooner thrombolysis is performed, the better. But it is naïve to think that time on a watch and a noncontrast CT scan should be the criteria for treatment. I have great difficulty understanding why the present thrombolytic guidelines are still based on a NINDS study planned nearly two decades ago that used now-outdated imaging criteria just because it was a randomized trial. Many volumes of experience with IV, intra-arterial, and combined IV/IA thrombolysis have followed that trial.

The brain and its functions and brain ischemia are complex. Treatment by stroke neurologists in centers that have the technology, personnel, and protocols to accomplish treatment surely is the goal. The brain is the Rolls-Royce of the body. Would you and I take our Rolls to a local gas station for repair? The challenge is to figure out how to get eligible patients (personally or by telemedicine) to properly equipped centers and to develop more such centers.

— Louis R. Caplan, MD

Dr. Caplan is Professor of Neurology, Harvard Medical School, Boston.

Published in Journal Watch Neurology April 24, 2007

Citation(s):

Albers GW et al. Magnetic resonance imaging profiles predict clinical response to early reperfusion: The diffusion and perfusion imaging evaluation for understanding stroke evolution (DEFUSE) study. Ann Neurol 2006 Nov; 60:508-17.

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