A second stroke may offer a path to successful rehab well after the usual window of opportunity from a prior disabling stroke has closed.
In experiments with mice, scientists found that starting a rehabilitation program immediately after the second attack, combined with certain other factors, helped promote recovery of motor function the animals had lost after the earlier stroke.
The investigators say the experiments do not and will never make a case for purposefully causing a second stroke in a human. But the research does suggest the mammalian brain may be far more “plastic” in such patients, they say.
Safe and ethical ways might be found to better exploit that plasticity and reopen the recovery window for disabled stroke victims who never regained full control of their motor movements.
“If we can better understand how to reopen or extend the optimal recovery period after a stroke, then we might indeed change how we treat patients for the better,” says Steven Zeiler, assistant professor of neurology at Johns Hopkins University School of Medicine.
According to the Centers for Disease Control and Prevention, stroke is the No. 1 cause of disability in the United States and costs $34 billion a year in in health care, medications, and missed days of work.
“Our study adds new strong and convincing evidence that there is a sensitive period following stroke where it’s easiest to relearn motor movements—a topic that is still debated among stroke researchers,” Zeiler says.
For the study, published in the journal Neurorehabilitation and Neural Repair, researchers taught mice to reach their front paws out of a cage to grasp food pellets on a bar, a task that four-legged animals don’t naturally perform. On average, the mice grabbed the pellets just over half of the time.
The researchers then induced a stroke in the motor cortex of the mice brains, making them unable to perform the task. After waiting well beyond the known “optimal” window for rehab training to begin, they put the mice through almost three weeks of training. The mice learned to grab pellets again, but only about 30 percent of the time.
The study’s next phase built on research showing that brain ischemia—the cutoff or reduction of oxygen to the brain during a stroke—under certain conditions increased plasticity, the brain’s ability to compensate for injury and form new neural connections.
The scientists induced a second stroke in the lab mice either in the secondary motor cortex near the first stroke site or, for a control group, in the visual cortex, far from the original site.
This time, the investigators began retraining the mice the day after the second stroke. Mice with the follow-up stroke in the motor cortex relearned to grasp food pellets as well as they did before the first stroke, with success more than 50 percent of the time.
Mice in the control group never did any better, even with extended training, suggesting that the motor cortex may be the only part of the brain with this type of “reopening” capability for motor movements.
Zeiler plans to investigate other ways to reopen the window of recovery and make use of the optimal recovery window. Earlier Johns Hopkins research found that a mouse’s window of recovery could be extended with the common antidepressant fluoxetine, given immediately after the stroke.
Other researchers from Johns Hopkins and from Duke University and UCLA are coauthors of the study. The National Institutes of Health and the James S. McDonnell Foundation funded the work.
Source: Johns Hopkins University