In an "unprecedented" clinical trial, U.S. researchers have successfully reversed the long-term debilitating effects in some of the stroke patients by injecting stem cells directly into their brains.
"This wasn't just, 'They couldn't move their thumb, and now they can,'" lead author Gary Steinberg, professor and chair of neurosurgery at the Stanford University School of Medicine, said in a statement.
"Patients who were in wheelchairs are walking now," said Steinberg, who led the 18-patient trial and conducted 12 of the procedures himself.
The small study, published this week in the U.S. journal Stroke, was designed primarily to test the procedure's safety, but the promising results set the stage for an expanded trial now getting underway.
The therapy involved drilling a small hole into the patients' skulls to allow for the injection of stem cells, accomplished with a syringe, into a number of spots at the periphery of the stroke-damaged area, which varied from patient to patient.
The stem cells, called SB623, are derived from the bone marrow of adult donors and modified to beneficially alter the cells' ability to restore neurologic function.
The patients, whose average age was 61, remained conscious under light anesthesia throughout the procedure, and the next day they all went home.
All the patients had suffered their first and only stroke between six months and three years before receiving the injections.
In each case, the stroke had taken place beneath the brain's outermost layer, or cortex, and had severely affected motor function. For example, some patients couldn't walk and others couldn't move their arm.
The results showed that all these patients showed significant recovery by a number of measures within a month's time, and they continued improving for several months afterward, sustaining these improvements at six and 12 months after surgery.
No relevant blood abnormalities were observed. Some patients experienced transient nausea and vomiting, and 78 percent had temporary headaches related to the transplant procedure.
"Patients improved by several standard measures, and their improvement was not only statistically significant, but clinically meaningful," Steinberg said.
"Their ability to move around has recovered visibly. That's unprecedented. At six months out from a stroke, you don't expect to see any further recovery."
Interestingly, the study showed that the implanted stem cells begin to disappear about one month after the procedure and are gone by two months.
That meant something secreted by these cells during their early postoperative presence near the stroke site stimulates lasting regeneration or reactivation of nearby nervous tissue.
The study also revealed that the stroke patients' postoperative improvement was independent of their age or their condition's severity at the onset of the trial.
"Older people tend not to respond to treatment as well," Steinberg said. "But here we see 70-year-olds recovering substantially."
The researchers also called for new thinking regarding the permanence of brain damage.
"The notion was that once the brain is injured, it doesn't recover -- you're stuck with it," Steinberg said. "But if we can figure out how to jump-start these damaged brain circuits, we can change the whole effect."
Some 800,000 people suffer a stroke each year in the United States alone, with about 85 percent of these strokes being ischemic in nature.
Although approved therapies for ischemic stroke exist, to be effective they must be applied within a few hours of the event -- a time frame that often is exceeded by the amount of time it takes for a stroke patient to arrive at a treatment center.
