HOPE FOR STROKE PATIENTS
Spinal cord stimulation device increases mobility in clinical trial led by Pitt and CMU
By the time Heather Rendulic was 24, she’d suffered five strokes, leaving the left side of her body fully paralyzed. Though she learned to walk again after years of painstaking physical and occupational therapy, her left arm and hand remained frozen.
Then she signed up for an experimental treatment that promised to restore movement in her arm through electrical stimulation.
The clinical trial, led by researchers from the University of Pittsburgh and Carnegie Mellon University, used remotely controlled electrodes implanted in the spinal cord to help Rendulic and one other patient once again move their arms. For the first time in years, Rendulic could complete daily tasks with her left arm, like picking up a can and turning a key.
“It was one of the best experiences of my life. It was surreal,” says Rendulic, a Shaler resident who’s now 33. “I was moving my left arm and hand in ways I hadn’t moved in almost a decade.”
The new treatment helps stroke patients move again by amplifying the natural electrical signals in their nervous system.
“Normally, our brain controls movement by sending signals from the brain to the spinal cord,” says Marco Capogrosso, an assistant professor at the Department of Neurosurgery at the University of Pittsburgh and an author of the study. But, after a stroke, “those cables that connect the brain from the spinal cord get broken.”
When the signal in the remaining few “cables” is too weak to generate nerve impulses in the spinal cord, stroke patients lose their ability to move the affected limb.
But in this new treatment, two long, thin electrodes — dubbed “spaghetti leads” by the researchers due to their shape — help generate extra electrical activity in the patient’s spinal cord. These “spaghetti leads” are surgically implanted in the section of the spinal cord that controls the muscles of the arm and hand.
Capogrosso says the surgery is minimally invasive, and is relatively similar to the procedure used to administer epidural anesthesia to women in labor.
The “spaghetti leads” are then switched on using a remote stimulator, which delivers a constant, low-level electrical current to a patient’s spinal cord.
That extra stimulation is just enough to augment the patient’s own electrical impulses from the brain; as soon as the stimulator device was switched on during the trials, in 2021, both patients could move their arm and hand in ways they hadn’t been able to since before their strokes.
Without the treatment, says Rendulic, “It’s kind of like there’s a disconnect between my brain and the muscles in my arm and hands. … but then during the trial, when the simulation was on, it was like I could feel that connection being restored.”
During the clinical trial, Rendulic and the second patient spent hours in the lab every day for four weeks, hooked up to
the external stimulator. Researchers monitored how their motor abilities changed and their capabilities to complete basic tasks grew.
By combining the stimulation with a physical and occupational therapy regimen, “they basically can improve more and more every day,” says Elvira Pirondini, an assistant professor of physical medicine and rehabilitation and bioengineering at PitT and a co-author of the study.
Out of the two patients, both recovered some motion in their arm after the procedure. Rendulic regained the ability to use her hand for daily living activities like simple writing and opening locks, while the other patient recovered general movement but no fine motor skills.
The researchers were also surprised to find that, even after the stimulation had been turned off, the patients retained some of the extra functionality in their arm and hand for a short time.
The treatment is one of many in the rapidly expanding field of nerve stimulation. Similar to how a pacemaker uses electrical stimulation to regulate contractions of the heart, nerve stimulation treatments use electricity to restore or modulate function in the nervous system.
“The use of electrical stimulation to treat neurological deficits has been around since the ’50s,” says Douglas Weber, a professor in the mechanical engineering department and the Neuroscience Institute at CMU and study co-author.
He explains that the cochlear implant, a device that helps translate sound waves into neural impulses so that a deaf person can hear better, was one of the first nerve stimulation devices.
Brain stimulation has also become a mainstay in Parkinson’s treatment. In a procedure called deep brain stimulation, electrodes are placed in some of the inner
movement circuits of the brain to reduce tremors.
Weber says that neural stimulation offers many benefits over other forms of treatment, particularly pharmaceuticals.
“Drugs affect neural signaling in the body, much like electrical stimulation does,” he says. “But there are many advantages to using electrical stimulation over, say, a drug that may enhance movement.”
One of those advantages is that electrical stimulation is much more precise than pharmaceutical treatment. Electrical impulses can be delivered to a specific place in the body and then switched on and off as needed, whereas pharmaceuticals will be absorbed everywhere and stay active until fully metabolized.
Weber says there are two main approaches in neural stimulation research. The first involves developing new technology that delivers electricity in new and improved ways, while the second concerns using existing technology and developing new targets in the nervous system.
The research in this trial falls into the second camp. “We’re using fairly well established
devices, but we’re applying them to a different location in the nervous system,” says Weber.
In their limited clinical trial, the researchers encountered no unpleasant side effects or complications, but they add that they still need to test the treatment in more patients and for longer time periods before they can be sure. And though their initial results are promising, there’s still a lot more work to do.
“We need to follow up with a longer study to understand who responds better to the stimulation, and how much will these people improve,” says Capogrosso. Future research will explore more permanent stimulators and embedded control devices, as well as what type of paralysis can be treated.
Rendulic didn’t want the trial to end, but she’s still excited for what the future holds. “I think the technology they’re working on is just so vital, and I think it’s just going to change the world.”