Two stroke survivors regain arm movement after implanted electrodes stimulate their spines

A stroke left Heather Rendulic with little use of her left hand and arm, putting certain everyday tasks out of reach.

“I live one-handed in a twohanded world, and you don’t realize how many things you need two hands for until you only have one good one,” the Pittsburgh woman said.

So Rendulic volunteered for a first-of-its-kind experiment: Researchers implanted a device that zaps her spinal cord in spots that control hand and arm motion. When they turned it on, she could grasp and manipulate objects.

It’s not a cure — the improvements ended after scientists removed the temporary implant — and the pilot study included only Rendulic and one other stroke survivor. But the preliminary results, published last week, mark a step toward restoring mobility for this common type of paralysis.

“They’re not just getting flickers of movement. They’re getting something important,” said Jason Carmel, a Columbia University neurologist who wasn’t involved with the new experiment but also studies ways to recover upperlimb function.

Nearly 800,000 people in the United States suffer a stroke each year. Even after months of rehabilitation, well over half are left with permanently impaired arm and hand function.

Experiments by multiple research groups have found that implanting electrodes to stimulate the lower spine shows promise for restoring leg and foot movement to people paralyzed after a spinal cord injury. But upper-limb paralysis has gotten little attention and is more challenging. The brain must signal multiple nerves that control how the shoulder lifts, the wrist turns and the hand flexes. Stroke damage makes it harder for those messages to get through.

“People still retain some of this connection, they’re just not enough to enable movement,” said Marco Capogrosso, a University of Pittsburgh assistant professor who led the new research with colleagues at Carnegie Mellon University. “These messages are weaker than normal.”

His idea: Stimulate a pathway of related nerve cells so they’re better able to sense and pick up the brain’s weak signal. “We’re not bypassing their control. We’re enhancing their capabilities to move their own arm,” he said.

Researchers turned to implants the size of spaghetti strands that already are used to stimulate the spine for chronic pain treatment. The implants carry electrodes that are placed on the surface of the spinal cord to deliver pulses of electricity to the targeted nerve cells, in the case of the arm and hand in the spine’s neck region.

Rendulic and a second, more severely impaired volunteer could move better as soon as the stimulator was switched on — and by the study’s end showed improved muscle strength, dexterity and range of motion, researchers reported in the journal Nature Medicine. Surprisingly, both participants retained some improvement for about a month after the implants were removed.

With National Institutes of Health funding, Capogrosso is studying the approach in a few more stroke survivors. The researchers also have formed a company to further develop the technology.