When providing initial treatment for a stroke, physicians face a dilemma: They have no easy way to determine which portions of the brain affected by the stroke could benefit from treatment and which areas are already lost. The distinction is critical; physicians can administer clot-busting drugs to restore blood flow and save endangered brain tissue, but these drugs carry a risk of unwanted bleeding. Doctors do not want to impose that risk for tissue that has already died and cannot be saved.
“Right now, if we have a patient who presents within the first hours of a stroke, we have no practical way of knowing what’s living and what’s dead in the areas affected by the stroke,” says Jin-Moo Lee, MD, PhD, Washington University neurologist at Barnes-Jewish Hospital and director of the cerebrovascular disease section in the Department of Neurology. “As a result, we operate strictly by the clock, administering therapeutics if stroke is detected in the first 4 1/2 hours after it occurs. But this therapeutic time window is likely to vary between individuals.”
Positron emission tomography (PET) makes it possible to monitor the brain’s oxygen metabolism; if an area of the brain has stopped using oxygen, it is assumed to be dead. According to Lee, though, acquiring the PET scans takes a great deal of time, and delays can lead to further brain damage.
To provide a better option, researchers have recently developed a much quicker method of assessing brain oxygen metabolism, using magnetic resonance imaging (MRI) scans. In collaboration with Lee, Washington University neurologist Andria Ford, MD, is running a clinical study that will determine whether such scans will be able to predict when tissue can and cannot be saved.
“If successful, this will allow us to use a physiological parameter to help guide therapy based on individual variation, rather than the clock,” Lee says. “In doing so, it may make our treatment safer, preventing us from incurring the risk of added bleeding in patients who don’t have viable tissue to be saved and potentially extending the treatment for some patients beyond the current cutoff time.”