An EES implanted in the neck stimulates the musculoskeletal response of an older woman with a spinal-cord injury

Four can walk on their own without the EES being turned on. This sustained recovery suggests that the stimulation triggers remodelling of the spinal neurons to bring the locomotion network back on line.

The amount of hope given to people with spinal-cord injury is amazing, says a neurologist who studies the injury.

The overall decrease in neural activity at the site during rehabilitation reflects a learning process, says Courtine. “When you think about it, it should not be a surprise,” he says, “because in the brain, when you learn a task, that’s exactly what you see — there are less and less neurons activated” as you get better at it.

This type of direct evidence in people doesn’t exist with technology. Eiman Azim, a scientist at the Salk Institute for Biological Studies, says that the same neurons are responsible for the effect because they are similar to humans and mice.

In the latest study, surgeons implanted a pair of thin metal electrodes resembling spaghetti noodles along the upper region of the spinal cord in the neck to target populations of nerves that control arm and hand muscles. The stimulation system in the lab was connected to the skin cables outside.

Courtine says that identifying the nerves responsible for these functions is on his list of next steps now that he has a detailed molecular map to work with. He has also launched a start-up company — ONWARD, based in the Netherlands — to commercialize the technology. 70–80 people from the United States will be recruited for a new trial in 2024.

Over four weeks, Rendulic and the other patient performed a series of lab tests. Three years prior, the second patient, a 47-year-old woman with more severe deficits, had suffered a stroke. They carried out tasks like moving blocks, picking up marbles, grasping a soup can, and opening a lock. While Rendulic showed more improvement than the other patient, the stimulation boosted strength, range of movement, and function of the arm and hand in both women. The device did not hurt, even though Rendulic could feel a little vibration in her arm.

A stroke happens when blood supply in the brain is blocked or when a blood vessel bursts. A stroke can cause a number of impairments such as paralysis, weakness, or problems with speaking, thinking, or memory depending on the severity of the brain damage.

People with paralysis from stroke can’t move a certain muscle or group of muscles voluntarily. When the part of the brain that controls movement is damaged, it disrupts the transmission of messages between the brain and the muscles. The first few months after a stroke are usually when patients recover. There is little chance of further improvement after six months. The effects of stroke are usually permanent in this stage.

Researchers wanted to deliver electricity to nerve cells in the spine. The stimulation of nerve cells by the electricity helps send brain signals to the muscles they control.

Spinal cord stimulation is already used as a treatment for pain, and in 2018, separate research teams published a series of papers showing that it allowed a handful of patients paralyzed from spinal cord injuries to stand independently and walk with assistive devices for the first time in years. For upper-limb recovery, the stimulation of the spinal cord has been unexplored.

The day researchers turned the electrical stimulation on, Rendulic was able to fully open and close her left hand—something she couldn’t do before. She says that they were all in tears. “I was opening my hand in ways I hadn’t in almost a decade.”

The results will need to be replicated in a larger study, because it’s not clear which stroke patients will benefit most from the treatment.

The Long Journey of a Stimulator to Rendulic’s Hand: From a Preteen Horse to a Permanent Spinal Implant

As a teenager, Rendulic liked to run and ride horses. She had a lot of strokes because of blood vessels in her brain. The last stroke was the worst.

Rendulic was eventually able to move her arm and hand a bit. For example, she could close her hand, but not open it. As a result, she was unable to tie her own shoes, open a jar, or chop vegetables.

He says that they wanted to pick up on the weak signals and turn them into functional outputs so that a person could control their own hand.

Elvira Pirondini says she can see at first that she can’t do anything with her hand. She can reach the soup and grab the can when the stimulation is on.

Also, the effects diminished but did not disappear entirely when the stimulation was switched off. It’s not clear how long the changes to the circuits will last, but it suggests that the pulses are causing the changes.

The electrodes were removed from both patients at the end of the study. A permanent system that can be implanted will be developed by researchers.

Ordinarily, moving this sort of technology from the lab to widespread use takes many years. But the process is likely to move much faster in this case because the device used to stimulate the spine is already approved by the Food and Drug Administration for treating patients with chronic pain.

Rendulic says her experience has changed the way she views her future, and she hopes to be first in line to receive a permanently implanted stimulator.