[LUM#20] Independence at Your Fingertips

[LUM Magazine, Podcast] - Published on October 17, 2023 in Science and Society

Restoring functional use of their hands and wrists to people with quadriplegia—that is the miracle that Christine Azevedo and her colleagues at Inria¹ have achieved through selective neural electrostimulation. When science reaches out with a helping hand.

It had been more than two years since Maxime had held a glass of beer in his hand or reeled in his fishing line. Soon, he will eagerly turn the pages of his novel and be able to use the catheter that allows him to urinate on his own. Because Maxime is quadriplegic. For the past few weeks, he has been participating in a neural electrostimulation trial led by researcher Christine Azevedo, director of the Camin team, and is regaining with their help the abilities that had become impossible since his accident.

Thanks to the team led by orthopedic surgeon Jacques Teissier at the Saint Jean Clinic in Montpellier, scientists implanted two small electrodes in his arm, wrapped around his nerves. “These are epineural electrodes, ” explains the researcher. “They will send electrical stimulation to the nerves, which will activate the muscles of the hand and wrist to generate movement. ” The process seems simple, yet it is the result of ten years of research.

Left behind

It all began when the American company that developed the Freehand system in the 2000s decided to shut down. “This system involved implanting electrodes in the forearm muscles that were connected to an implant, allowing the user to open and close their hand by moving their shoulder, for example,” the researcher explains. Overnight, the 250 quadriplegic patients with the implant found themselves left in the lurch. Among them, some had been operated on by Jacques Teissier and were being treated by Charles Fattal, chief physician at the Bouffard-Vercelli Functional Rehabilitation Center in Perpignan. Together with Christine Azevedo and the two Inria researchers, David Andreu and David Guiraud, they form the team behind a new method of neural electrostimulation.

“One of the drawbacks of the Freehand system was that it required implanting an electrode in each of the eight muscles of the forearm. We wanted something less invasive,” recalls the researcher. “Within the team, David Guiraud had already been working on neural stimulation to restore walking ability in paraplegics” ( read: A Giant Leap for Prosthetics). Adapted for the upper limbs, this approach makes it possible to activate all the muscles of the forearm by implanting just two electrodes: one on the radial nerve and the other on the median nerve. The problem: since these nerves control all the muscles, how can stimulation be targeted to generate only the desired movement?

28 days…

“The challenge was to successfully activate specific segments of the nerve to enable useful movements,” confirms Christine Azevedo. The unique feature of the epineural electrodes manufactured by the German company Cortec is that they wrap around the nerve to provide multiple contact points. Following a successful initial phase of experimentation on rabbits, nine orthopedic surgery patients agreed to allow the team to use their arm surgery as an opportunity to implant electrodes, test them, and remove them before the patients woke up. “We observed that by activating different contact points around the nerve, we could generate very specific movements: closing all the fingers, extending the wrist…”

It is 2020, and the Camin team and its partners are preparing for Phase 3 of the project, which will be called Agilis and later Agilstim: implanting neural electrodes in four patients for 28 days. In the meantime, the COVID-19 pandemic erupts, and only two patients participate in this trial before two others join them in 2023. To allow them to trigger the movement themselves, the electrodes are connected by two cables to a stimulator located outside their bodies. “Patients control it using various types of controls: buttons they press with their elbow or head, a sensor on the shoulder that converts movement or muscle contraction into a signal, voice commands…”

Like the back of my hand

For 28 days, researchers and patients meet three or four times a week to test the device. First, the stimulator must be configured to determine which muscles are activated by each of the electrode’s contact points, as nerve configurations vary from patient to patient. This is followed by sessions designed to elicit specific movements: five prescribed tasks and five tasks chosen by the patients themselves. “The first patient wanted to brush his teeth on his own and, above all, turn a doorknob because he had previously found himself stuck. Another wanted to be able to sign documents or plug in a USB drive. Not everyone attaches the same meaning to these gestures, but what’s at stake is a form of autonomy. ” And they all succeeded! “These are very powerful moments. Scientifically, we’re having fun, but the heart of it is them—it’s the human element,” emphasizes Christine Azevedo.

In 2025, four new patients will receive the implant. The Montpellier-based startup Neurinnov, founded in 2018 by David Andreu and David Guiraud to commercialize and bring to fruition their research on selective neural stimulation, is working on developing a stimulator that can be implanted directly into patients’ bodies. In 2026, new trials will be conducted to validate this implant and proceed to CE marking and market launch. For Maxime, the 28 days have since passed and the electrodes have been removed from his arm, but he knows that the years separating him from a permanent implantation of this device can now be counted on one hand.

1. *Lirmm (UM, CNRS, Inria, UPVD, UPVM)
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Keywords: Body, LUM#20, LumLu, LUM Magazine, Movements, Research, Science, Company