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. 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," 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," Bloch said of the participants' progress.
Courtine and Bloch now plan to work with Onward Medical to make the device more user-friendly for everyday use, such as integrating the program with cellphones 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 Center, 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." (CNN)
