Michel Roccati lost the ability to walk after a motorcycle accident in 2017, when he had a complete spinal cord injury.
But today, equipped with an electrode device implanted on his spinal cord, Roccati can enjoy the simple things again: standing at a bar for drinks with friends, taking a shower without a chair and even strolling through the town with a walker.
"I am free," Mr Roccati, who is from Italy, said. "I can walk wherever I want to."
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Mr Roccati was one of three men between the ages of 29 and 41 to participate in the STIMO clinical trial, led by Dr Jocelyne Bloch from Lausanne University Hospital and Grégoire Courtine of the Swiss Federal Institute of Technology. The results of the study were published Monday in the journal Nature Medicine.
The participants had 16-electrode devices implanted in the epidural space, an area between the vertebrae and the spinal cord membrane. The electrodes receive currents from a pacemaker implanted under the skin of the abdomen.
All the patients in the trial had a complete loss of voluntary movement below their injuries. Two also had a complete loss of sensation. But with the devices in place, the researchers could use a tablet computer to initiate unique sequences of electrical pulses, sent to the epidural electrodes via the pacemaker, to activate the participants' muscles.
Other studies have anecdotally seen movement soon after surgery to implant similar devices, but this is the first study to report that all participants independently could take steps on a treadmill just a day after surgery, the researchers said.
"It's a very emotional moment, because [patients] realise they can step," Dr Bloch said.
Researchers have been looking into electrical stimulation to the spinal cord for three decades. This study redesigned technology originally used to alleviate pain to target spinal nerve roots.
Previous studies out of the University of Louisville have shown that people who were completely paralysed but still had sensation could walk again with several months of rehabilitation through electrical stimulation to the spinal cord.
The STIMO trial found that within a week of their surgeries, all three participants could walk independently with the use of body-weight support from parallel bars and an overhead harness.
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"For the first time, we have not only immediate effect – though training is still important – but also individuals with no sensation, no movement whatsoever, have been able to regain full standing and walking independently of the laboratory," Mr Courtine told CNN.
Dr Nandan Lad, a neurosurgeon at Duke University, said this "very exciting work gives a new treatment option for tens of thousands of patients that have spinal cord injury and don't really have other options."
Dr Lad is leading a clinical trial in this area of research in the US and was not involved in the new study.
The Swiss team has been able to observe immediate results through important changes in the structure and implantation of their electrode device.
The electrode array used in the STIMO trial, made by Onward Medical, is wider and longer than the array most commonly used in similar studies.
According to Bloch, this new electrode array allows access to a broader area of the spinal cord to stimulate both trunk and leg muscles.
The investigators developed an algorithm to optimally place the electrode array, running tests during the surgery to measure muscle activity after delivering pulses. The precise neurosurgical placement of the electrodes is key to the study's ability to stimulate the necessary muscle groups in the legs so quickly, Dr Lad said.
The STIMO trial also introduces a new method for initiating and sustaining movement. To begin stimulation, previous studies have relied on participants' intent to move and the brain signals that follow.
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In the new study, a timed sequence of stimulations is generated using motor responses to different jolts of electricity. These pre-established sequences trigger movement and attempt to mimic the natural pattern of muscle activation needed to walk.
Susan Harkema, a professor in the Department of Neurological Surgery who led the Louisville studies, said it's encouraging to know that two types of stimulation can generate movement patterns through human spinal circuitry, indicating that some function is retained, even with complete injuries.
"But I don't think we have enough evidence yet to know the best way to stimulate for the best outcomes," Ms Harkema told CNN.
With the STIMO device, people with complete spinal cord injury can regain voluntary movement in their legs only while receiving stimulation. While the device is off, voluntary movement will not be possible. The electrodes can remain in place for life, but the pacemaker needs to be replaced every nine years.
But with training, patients can build up greater endurance and do a wider range of activities. After the surgery, the study participants received one or two hours of physical therapy four times a week.
With three or four months of consistent training, one participant could stand for two hours at a time. Another could walk 500 meters independently. One participant even climbed stairs again.
The tablet used in the study comes equipped with specific programs coded for certain types of activity, including standing, walking, and swimming.
"The more they train, the more they achieve, so they need the motivation to be able to stand a long time," Dr Bloch said of the participants' progress.
Mr Courtine and Dr Bloch now plan to work with Onward Medical to make the device more user-friendly for everyday use, such as integrating the program with mobile phones or smartwatches.
Next, the team is looking to scale up to a larger clinical trial in the US. They estimate that it will take another three or four years for the technology to become commercially available.
In a press briefing last week, the researchers announced that the US Food and Drug Administration has approved a "breakthrough devices" designation to expedite the process.
This designation would also ensure coverage through the Medicare Coverage of Innovative Technology program if larger clinical trials are successful.
"I think [this research] should be a call for all of us to understand that there is hope for the treatment of these patients," said Dr Nicholas Theodore, director of the Johns Hopkins Neurosurgical Spine Centre, who was not involved in the research.
"I think the hope right now is going to be through an engineering solution and less so than cellular reparative strategy."
