NEW YORK (Reuters Health) – Stroke patients with a lesion that is larger on perfusion-weighted MRI than on diffusion-weighted imaging–a so-called PWI-DWI mismatch–are most likely to benefit from thrombolytic therapy up to 6 hours after stroke onset.
That is according to results of a prospective study reported in the January Annals of Neurology. Dr. Geoffrey A. Donnan, of the Austin and Repatriation Medical Center, Melbourne, and colleagues analyzed serial diffusion- and perfusion-weighted MRI patterns in 19 stroke patients before thrombolysis with tissue plasminogen activator, subacutely, and at outcome. Twenty-one ischemic stroke patients studied serially with PWI/DWI, but who had not received tPA, served as a historical control group.
The PWI-DWI mismatch pattern was present in 16 of 19 patients treated with tPA and 16 of 21 controls. PWI-DWI mismatch patients treated with tPA had greater vessel recanalization, enhanced reperfusion, and less infarct expansion compared with untreated controls, the team reports. This translated into improved clinical outcome.
The findings suggest to the authors that the "natural evolution of acute PWI-DWI mismatch tissue may be altered by thrombolysis, with improved stroke outcome." They propose that the presence of a non-mismatch pattern should prompt a "reevaluation of whether a patient should receive thrombolytic therapy, particularly if a large diffusion lesion is present."
In comments to Reuters Health, Dr. Donnan noted that "this is first evidence that we may be able to select patients for thrombolytic therapy more precisely by using MRI." He and Dr. Stephen M. Davis, a co-author on the Annals paper, are spearheading a randomized controlled trial designed to evaluate their observations more rigorously.