Research Offers Hope for More Effective Stroke Treatments
Many of the statistics about stroke are troubling. The disorder is the third leading cause of death in the world. And, because stroke risk rises sharply after age 60, countries with large "boomer" populations, such as the United States, are on course for a substantial increase in stroke prevalence in upcoming decades.
There are two bright spots on the horizon, however, Walter Koroshetz, deputy director of the National Institute of Neurological Disorders and Stroke, explained at a 22 May Capitol Hill briefing hosted by AAAS in conjunction with Rep. Chaka Fattah (D- Pa.) and with support from the Dana Foundation.
For one thing, up to 70% of strokes are preventable by fairly simple measures such as blood pressure control, improved diet and exercise.
"The data for stroke show that if we really got our act together, we could make a huge difference because the science tells us that one's annual stroke risk decreases dramatically as known risk factors are controlled." Koroshetz said. "If we achieve optimal weight control, physical exercise, blood pressure and diet earlier in life, then the health benefits to individuals, their families and to the country as a whole would be enormous."
A central understanding in this research field is that when one part of the brain dies in a stroke, another part of the brain can "learn" to take over its function. Much of what scientists are learning about this dynamic rewiring of the brain comes from studying brain development in childhood, when connections between brain cells are being formed, strengthened or pruned at an astounding rate as the child interacts with the environment.
"The stimulus the brain is getting has a lot to do with the rewiring," Koroshetz said. That same principle applies in the treatment of stroke, where neural development patterns that have been suppressed since childhood can start working again and be enhanced and molded by intensive rehabilitation therapy. He noted an Emory University-led study with stroke patients who had a disabled arm. With their good arms immobilized, the patients gained dexterity in the affected arm, including some who started the treatment regime as long as 21 months after their strokes.
As scientists learn more about these intrinsic repair processes, they are finding more potential targets for drug therapies. But most relevant for patients right now, Koroshetz said, are the efforts to improve standard rehabilitation care. He noted a clinical trial of stroke patients from five hospitals in Florida and California which showed that intensive rehabilitation, either with in-home exercises or on a treadmill, led to improved walking ability as compared to "standard of care" rehabilitation. Even six months after their strokes, patients who had received only the standard care could still make substantial improvements in walking by undergoing intensive treadmill training.
"This tells us that our standard of physical and rehabilitation therapy after a stroke is not optimal," said Koroshetz. Patients often can benefit from more intensive therapy regimes, he said.
New technologies also offer promise. Koroshetz noted work with brain-machine interfaces using implanted electrodes that can record neuronal signals in the motor cortex of the brain. In a study reported last year, a woman paralyzed by a stroke learned to use her thoughts to generate neuronal signals to steer a robot arm to grab a bottle of coffee and lift it to her lips.
Other researchers have developed "therapeutic exoskeletons," motor-powered mechanical braces that do much of the work of walking or lifting. The devices can help patients carry out the intensive activity they need to perhaps trigger some of the brain's intrinsic repair mechanisms.
New recording technologies, such as optical probes that can detect tiny flashes of light by thousands of firing nerve cells, offer new possibilities for listening in on the electrochemical "language of the brain," Koroshetz said. The BRAIN Initiative (Brain Research through Advancing Innovative Neurotechnologies), announced recently by President Barack Obama, should greatly expand the amount of information scientists can glean from these new technologies.
On the rise. The World Health Organization projects that deaths due to cardiovascular disease, including those caused by stroke, will continue to rise if appropriate measures are not taken. [Source: A Global Brief on Hypertension, World Health Organization]