This story is part of a partnership between MedPage Today and VICE News.
When researchers at Stanford University injected stem cells into the brains of stroke victims for a recent study, they were surprised to see that some patients regained mobility, a stunning development since stroke damage is usually permanent. But experts — including the study authors themselves — caution "overselling" these results.
Dr. Gary Steinberg, chair of neurosurgery and the co-director of the Stanford Stroke Center, and his colleagues were only testing to see whether the injections were safe, which is how phase one clinical trials usually work. Efficacy trials come later, but the researchers found that more than half of the chronic stroke patients in their small study showed improvement in mobility, according to findings published this week in the medical journal Stroke .
A 71-year-old patient who had only been able to use her thumb and couldn't get out of bed before the trial was able to walk after receiving the stem cell injection, Steinberg said. A 39-year-old woman who didn't want to marry her boyfriend because she couldn't talk or walk down the aisle has improved so much that she's gotten married and is expecting a baby.
"We did not expect these impressive clinical results," Steinberg said, stressing that it was a small study designed to look at safety and search for a "hint" about the efficacy of stem cell treatment. "We're very encouraged, and we want to explore a larger study."
Although the study offers hope for thenearly 800,000 people who have strokes every year, Steinberg stressed that stroke patients shouldn't expect to return to normal with stem cell treatments.
Dr. Cathy Sila, a neurologist and stroke specialist at University Hospitals Case Medical Center in Ohio who was not involved in the study, said to remember that the study participant who walked down the aisle at her wedding is a promising anecdote, but an anecdote nonetheless.
"We just need to stick with the science," Sila said. "This trial was not designed to look at any of that. It was purely a safety study in a small number of patients."
Steinberg and his team chose 18 patients who had sustained ischemic strokes resulting in motor function problems. Ischemic strokes are the most common type of stroke, and they're caused by a blocked artery, which prevents oxygen-rich blood from getting to the brain.
The average age of the patients was 61 years old, but they ranged from 33 to 75. They had suffered strokes between six months and five years prior to the start of the study.
The stem cells used in the study came from the bone marrow of human donors, rather than from the patients' own bone marrow, but prior studies showed that rejection wasn't a concern and there would be no need for immune system suppression, Steinberg said.
'They turn the adult brain into a neonatal or infant brain, which we know recover well from stroke and other injuries.'
Patients were awake but sedated as the doctors used brain mapping equipment to find the precise areas of the brain surrounding the stroke — areas with no blood flow — and inject the stem cells through a few tiny holes.
The stem cells don't last forever, and they don't turn into neural cells as scientists first suspected more than a decade ago, Steinberg said. Instead, animal studies that preceded this human study showed that the stem cells stick around for one or two months, and seem to "jump-start" the brain's healing process by pumping out molecules and proteins that enhance the brain's existing mechanisms for recovery.
"They turn the adult brain into a neonatal or infant brain, which we know recover well from stroke and other injuries," Steinberg said.
Although the researchers were only testing for safety, they included several different scales to measure whether mobility improved as part of their study design to "get a hint" about what efficacy studies would yield later on.
According to the Fugl-Meyer scale, which is used to measure mobility improvement, seven patients improved by more than 10 points, "meaning it changed their life," Steinberg explained. It's now been two years since the start of the study, and the patients' improvements are still present.
Sila stressed that the study was still very preliminary. The study participants' conditions and time since their strokes varied widely, she said. And it's unclear from the study whether any other factor could have contributed to mobility improvements, she said. She added that one of the scales Steinberg's team used to measure patients' improvement, the modified Rankin Scale, didn't yield any significant positive changes.
"I don't want people to get the idea that we've solved the problem, that this will make them walk again after stroke," Sila said. "The data does not demonstrate that."
All patients in the study experienced some adverse event, the study showed, but these were mostly headaches from the procedure, nausea, vomiting, and depression. Increasing the dose did not seem to increase the symptoms, and these symptoms weren't definitely related to the stem cell treatment.
"There's enough hope and a signal that we might be heading in the right direction, but we really need a large, randomized, placebo-controlled trial," Sila
A larger study with a control group is already in the works, Steinberg said.
Follow VICE News on Twitter: @slupkin