Magnetic resonance imaging can help distinguish which patients with unclear-onset strokes might benefit from clot-busting drugs while facing acceptable risk, according to research presented at the American Stroke Association’s International Stroke Conference 2011.
In the research, funded by the Korean Health Ministry of Health & Welfare of the Republic of Korea, Dong-Wha Kang, lead author, and colleagues used magnetic resonance imaging techniques to screen 430 patients with unclear-onset stroke at six university hospitals in South Korea.
“Wake-up, or unclear-onset, strokes account for a quarter of all ischaemic strokes but have been automatically excluded from clot-busting techniques because the onset time cannot be known. Our study shows that such patients could also be treated safely and effectively,” said Kang, who is also associate professor in the department of Neurology at Asan Medical Centre at the University of Ulsan College of Medicine in Seoul, South Korea.
All the patients researched arrived to the emergency rooms within six hours of detecting symptoms. Using diffusion-perfusion magnetic resonance imaging, the researchers looked for sizable areas where tissue remained alive even though it lacked blood flow.
To limit the risk of serious bleeding in the brain from clot-busting therapy, patients were excluded if they had extensive tissue death in the brain area supplied by the middle cerebral artery, or if other magnetic resonance imaging techniques, such as FLAIR or T2, showed that the time of tissue death had elapsed.
As a result, more than 80 patients (median age 67 and classified as having severe stroke) were found eligible for clot-busting therapy, which included intravenous administration of the drug tissue plasminogen activator (tPA) or direct administration of the drug urokinase. Some patients also had their clots removed mechanically or underwent stenting.
Among those who received the drug therapy, about 45% had at least a “good” clinical outcome—ranging from no symptoms to slight disability with curtailed activities—on the modified Rankin scale. Almost 29% had an excellent clinical outcome.
A key limitation of the study is it did not include a comparison group of patients who did not receive the clot busting treatment. Still, Kang said, “This study should trigger follow-up studies to develop the best available treatment strategies for this important but neglected group of stroke patients.”
The study also found that female patients were likely to fare more poorly with treatment, as were patients who had a more severe initial assessment of their stroke impairment, and those treated at the two centres lacking previous experience in thrombolysis for unclear-onset stroke.
Because researchers in the study treated patients with strokes of various origins, it is likely that the findings would also apply to non-Korean populations, said Kang. But patient outcomes are likely to vary among medical centres, due to the availability of magnetic resonance imaging facilities as well as interventionists to deliver clot-busting drugs directly to the brain blood vessels.
This work received the Emergency Medicine Award from the International Stroke Conference committee – which recognises outstanding research in the field by a young investigator.
The research team next plans to compare the outcomes from their study population with those of comparable but untreated patients listed in stroke registries. “Although this study provides some important clues to treat wake-up, or unclear-onset, stroke patients, we still have a long way to go to find the best way to treat them,” Kang concluded.
