A new magnetic resonance imaging (MRI) technique developed at the Stanford Stroke Center differentiates stroke patients who likely to benefit from a stroke medication – within or beyond the currently approved three-hour time window — and patients that are better off without treatment because it could prove harmful. The research was first reported in the November issue of Annals of Neurology.
Greg Albers, MD, leader of the team at the facility, has been using new MRI techniques to visualize the damage from stroke while it is actually happening. His goal has been to differentiate brain tissue that is potentially salvageable from tissue that already is irreversibly injured by a stroke. As his group accumulated MRI scans of stroke patients, they noticed patterns that seemed to identify which patients were most likely to benefit from opening up blocked blood vessels.
"One of the criticisms was that these detailed brain images looked beautiful and interesting, but there was no proof that they should be used to influence treatment or that they would result in improved outcomes," said Albers. "How do you know that these MRI patterns can predict whether the therapy is likely to be beneficial?"
The team designed a three-year study to see if obtaining an MRI profile from stroke patients before beginning treatment could identify which patients would benefit from clot-dissolving drugs administered between three and six hours after stroke onset and which patients were unlikely to benefit or that could be harmed.
The team enrolled 74 consecutive stroke cases and obtained MRI scans for each patient immediately before, as well as nearly four hours after, administration of intravenous tPA. The scans were analyzed later and the pre-treatment MRI patterns were compared to how the patients fared three months later.
Of those evaluated, three patients developed fatal cerebral hemorrhage following tPA treatment. All three had a unique MRI pattern prior to treatment and the successful opening of their blocked blood vessel after treatment. This led the investigators to define a new profile that predicts a high risk of dangerous bleeding in the brain following tPA therapy for that subset of patients.
Still, for those patients who had a pattern indicating that a favorable response to tPA was likely, the benefits of opening the blocked vessel were impressive. "Sixty-seven percent of these patients had a major improvement in neurological function," Albers said. "This often meant the difference between inability to speak with paralysis of one side of the body and a complete, or nearly complete, recovery."