[LUM#20] Autonomy at your fingertips

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

Restoring functional use of the hands and wrists to people with quadriplegia is the miracle that Christine Azevedo and her colleagues at Inria¹ have achieved thanks to selective neural electrostimulation. When science reaches out with its hand over its heart.

It has been more than two years since Maxime last held a glass of beer in his hand or reeled in his fishing rod. 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 several weeks now, he has been participating in a neural electrostimulation trial led by researcher Christine Azevedo, director of the Camin team, and is regaining movements 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 wrapped around his nerves in his arm. "These are epineural electrodes, " explains the researcher. " They send electrical stimulation to the nerves, which activate the muscles in the hand and wrist to generate movement. " The process seems simple, but 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 cease operations. "This system involved implanting electrodes in the forearm muscles connected to an implant that allowed the hand to be opened and closed by moving the shoulder, for example," summarizes the researcher. Overnight, the 250 quadriplegic people with the implant found themselves left behind. Some of them had been operated on by Jacques Teissier and were being monitored 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 quintet 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 worked on neural stimulation to restore walking in paraplegics ( read: A giant leap for prosthetics). Adapted for the upper limbs, it offers the possibility of activating all the muscles of the forearm by implanting only two electrodes: one on the radial nerve and the other on the median nerve. The problem is that since these nerves control all the muscles, how can the stimulation be specified to generate only the chosen movement?

28 days...

"The challenge was to successfully activate sub-sections of the nerve to achieve 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 various contact points. After a successful initial trial phase on rabbits, nine orthopedic surgery patients agreed to allow the team to implant electrodes during their arm surgery, test them, and remove them before they woke up. "We saw that activating different contacts around the nerve generated very specific movements: closing all the fingers, extending the wrist, etc."

It is now 2020, and the Camin team and its partners are preparing phase 3 of the project, which will be called Agilis and then Agilstim: implanting neural electrodes in four patients for 28 days. In the meantime, COVID-19 explodes and only two patients participate in this trial before two others follow in 2023. In order for them to trigger the movement themselves, the electrodes are connected by two cables to a stimulator located outside their bodies. "Patients control it using different types of commands: buttons that they press with their elbow or head, a sensor located on the shoulder that converts movements or muscle contractions into signals, voice commands, etc."

On the fingers of one 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 observe which muscles are activated by each of the electrode's contact points, as the configuration of nerves differs from one patient to another. This is followed by sessions aimed at producing specific movements: five imposed tasks and five tasks chosen by the patients themselves. "The first patient wanted to brush his teeth on his own and, above all, open a door handle, because he had already found himself stuck. Another wanted to be able to sign documents or plug in a USB key. Not everyone attaches the same meaning to these gestures, but what is at stake is a form of autonomy. And they all succeeded! "These are very powerful moments. Scientifically, we enjoy ourselves, but the heart of it is them, it's the human aspect," emphasizes Christine Azevedo.

In 2025, four new patients will receive implants. Montpellier-based start-up Neurinnov, launched in 2018 by David Andreu and David Guiraud to promote and implement their research on selective neural stimulation, is working on the development of a stimulator that can be implanted in patients' bodies. In 2026, new trials will be conducted to validate this implant and obtain CE marking and market authorization. For Maxime, the 28 days have now 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 the fingers of one hand.

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