LOS ANGELES—Use of diffusion-perfusion and FLAIR MRI to screen patients presenting with an unclear onset of stroke helps identify more such patients who might benefit from thrombolytic treatments such as t-PA, according to research presented at the 2011 International Stroke Conference. Nearly half of the patients who received these clot-busting therapies ultimately experienced a good clinical outcome.
Unclear-onset strokes, which include unwitnessed strokes and those occurring when a patient wakes up with symptoms, account for a quarter of all acute ischemic strokes, noted study author Dong-Wha Kang, MD, PhD. However, patients with unclear-onset strokes generally have been excluded from standard thrombolytic therapies due to their potential danger. Thrombolytic therapies are safer and more effective at reducing disability the sooner they are delivered, but they carry an increased risk of severe bleeding in the brain if delivered after 4.5 hours.
“Using various information given by MRI, we can pinpoint or narrow down the window of time of actual stroke onset,” said Dr. Kang. “The main purpose of the study was to see if the clot-busting treatment for those selected patients is feasible and results in acceptable safety and efficacy outcomes.”
Dr. Kang, Associate Professor in the Department of Neurology at Asan Medical Center at the University of Ulsan College of Medicine in Seoul, South Korea, and colleagues studied patients who presented with unclear-onset stroke at six medical centers in South Korea.
The prospective, multicenter, observational study included all patients who arrived at an emergency room within six hours of detecting symptoms. In total, 430 unclear-onset stroke patients were screened with diffusion-perfusion FLAIR MRI.
Screened patients were considered to be eligible for thrombolytic therapy if there was not extensive tissue death in the brain on diffusion MRI, if there was presence of sizeable areas where brain tissue remained alive despite lack of blood flow on diffusion-perfusion MRI, and if FLAIR imaging had shown that the time of tissue death had not elapsed.
Of the initial 430 patients who underwent MRI, 83 (median age, 67) were eligible to receive thrombolytic therapy. The three therapies that were used were IV administration of t-PA, direct administration of urokinase to the blocked vessels, and stenting or mechanical removal of the clot.
Clot-Busting Therapies Lead to Favorable Outcomes in Stroke Patients
“About 45% of patients had at least a ‘good’ clinical outcome,” Dr. Kang stated, meaning that the effects ranged from “no symptoms to slight disability with curtailed activities.” In addition, 29% of patients had an “excellent” outcome and were able to perform all their usual daily activities with little or no impairment.
“Serious bleeding in the brain with any neurologic decline occurred in 4% to 6% of those [who received thrombolytic therapy],” Dr. Kang said. In addition, 3.6% of patients had bleeding in the brain accompanied by an increase of four or more points on the NIH Stroke Scale. “These safety and efficacy outcomes are very comparable to those of the previous benchmark thrombolysis trials in clear-onset strokes,” he reported.
The investigators also identified patients who may be predisposed to a poor clinical outcome, including women and patients who presented with a more severe stroke at initial assessment. Patients treated at two of the six medical centers that lacked previous experience in thrombolysis for unclear-onset stroke also had poorer outcomes, indicating that experience played an important role in the success of clot-busting treatments, the researchers noted.
Importance of Findings for Treating Patients With Unclear-Onset Stroke
The researchers hope that their findings will allow physicians to select patients whose actual stroke onset time is close to the time when they initially report experiencing symptoms. “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,” Dr. Kang reported.
Dr. Kang pointed out several study limitations, mainly that there was no control group of patients who did not receive clot-busting treatment. Patient outcomes are also likely to vary according to the availability of MRI facilities and expertise of medical professionals.
“There is some controversy regarding the use of MRI in pinpointing the actual onset time of wake-up strokes,” he said, “because everybody uses slightly different criteria and different nomenclature about unclear-onset stroke.
“Our results won’t change the clinical process immediately, because this is not a randomized controlled trial,” Dr. Kang commented. “But our study will trigger the follow-up studies and warrants larger clinical trials … to prove the benefit of the treatment in wake-up strokes.”
—Ariel Jones