At the origin of this miracle is a team from Grégoire Courtine, from the Federal School of Applied Arts in Lausanne, who surgically implanted a network of sixteen subdural electrodes (the membrane that protects the spinal cord) into the lumbar vertebrae.
Once connected to the stimulator, the electrodes send electrical impulses to the part of the spinal cord that controls the leg muscles, and the legs begin to move until then.
But where this achievement was unusual and unprecedented, was that when the researchers pressed the “off” button on the pacemaker, two of the three patients rose up and walked again on their own! Definitely less good, and less stimulation time, but they have really regained use of their legs. As for the third, he managed to do some movements while lying down. As if the machine had returned them to control the keys to their limbs.
To understand these results, we must go back to the early 2000s, in Los Angeles, in the laboratory of Reggie Edgerton (University of California). The scientist, already known for his work on spinal cord injuries, is trying to find a way to get paralyzed mice to walk again, when he welcomed two young researchers, Gregoire Curtin and Susan Harkima. ” Between 2003 and 2007, we moved from the paralyzed rat to the mice being able to run on a treadmill, just by applying continuous electrical stimulation to the spinal cord. Gregoire Curtin recalls.
Draw some steps
Then the two young researchers left Los Angeles, one to Switzerland and the other to the University of Louisville in Kentucky. Excited about the results obtained on mice, Susan Harkima soon turned to human experiments. And in 2011 he published his first results: Rob, paraplegic after a traffic accident, was able to get up and take a few steps on a treadmill. Since then, Susan Harkima has implanted dozens of patients. In September 2018, the exploits of two of them were published: this time, they were able to walk again on the floor, without the wavy effect of the carpet.
On the same day these results were published, evidence of the intense competition taking place in this field, the team of Megan Gill and Christine Gao, at Mayo Clinic (Minnesota) Identical results were reported in another patient. However, Gregoire Curtin asserts, In these American patients, the effect stops once the stimulator is switched off, and the steps they were able to take under stimulation were Preceded by numerous rehabilitation sessions, sometimes for more than a year. Our patients were able to take their first steps only a few days after the electrodes were implanted. “.
A difference in size, according to the researcher, comes from the type of stimulus emitted. He realized that the portion of the spinal cord that controls the movements of the legs might be small and located only over 5 cm, but that there is a complex degree of gait. He records that he worked to decipher the code before running it on the electrodes. ” To play the piano, you have to press the right keys at the right time. Here it is exactly the same. To bend the hip, for example, we stimulate the L1-L2 region Gregoire Curtin explains.
Le signal amplifier
And if the results are better with this type of targeted stimulation, he says, it is because it offers several advantages. First, It does not replace the control of the brainInflates it. ” In those patients whose level of paralysis is not complete, there are few nerves that the information continues to circulate. By stimulating the spinal cord just as the brain does, we amplify the information left over from the brain, and this Accompanying and simulating information from the brain and electrodes that together stimulate walking “, Defines the researcher.
Another feature: unlike constant stimulation, Targeted stimulation does not block allergic informationThe ones that step up the foot and the leg to inform the brain of their location. Finally, even if this remains unproven, it will be the persistence of these sensory signals that allows the remaining nerve fibers to intensify their connections. It is this reorganization of the neural connections that would explain Gregoire-Curtin’s patients are able to walk … including the pacemaker turned off!
Admittedly, these patients were young athletes and had only partial lesions. However, they only walk with the aid of a walker or crutches, and they still use wheelchairs on a daily basis.
So it remains to be confirmed whether the method works for patients with more radical lesions. But the fact that Grégoire Courtine patients are able to walk even when the stimulator is turned off means that there is neuroplasticity, the importance of which has not been questioned. It is a miraculous discovery that gives us a bowl of hope. Sebastian is one of three patients Prof. Curtin’s team has followed.
From Science & Vie – Answers to Question 40