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 The technique is still experimental and relies in part on
implantation of electrodes that seem to prime the largely-dormant
part of the spinal cord to listen to faintly-echoed commands by the
brain to walk.
"We all walk independent of the brain in a sense because the human
spinal circuitry is the primary controller of walking," said Susan
Harkema, a leader of the team from the University of Louisville
whose report appears online in The New England Journal of Medicine.
Below the level of a spinal cord injury, hundreds of thousands of
nerve cells "are still alive and healthy and still connected in a
network that controls movement" and allows walking with minimal
input from the brain, she told Reuters Health in a telephone
interview.
The technique being used by her team re-energizes the walking
function, although the patients still need some support because all
the information needed to maintain balance -- sensory information
processed by the brain -- still has trouble getting through.
Like the other 1.27 million people paralyzed by a spinal cord injury
in the United States, all four volunteers described in the new
report were unable to walk or stand. All had been unable to move
their legs for at least 2.5 years, although they did have some
sensation below the site of their injury.
For at least eight weeks, each volunteer spent two daily one-hour
sessions, five days per week, on a treadmill with their weight
supported in a harness as physical therapists moving their legs and
feet in a walking motion. They were also trained to stand. That
therapy alone did not allow them to stand or walk.
A 16-electrode device used for pain control and not designed to help
paralyzed patients walk was then implanted between a bone in their
spine and the spinal cord, below the damaged area.
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After about 20 days to recover from surgery, the researchers worked
to find the right pattern and intensity of electrode stimulation to
activate standing and stepping movements as the volunteers focused
on trying to perform those tasks.
The third and fourth patients they enrolled, who received a
combination of electrical stimulation and gait training for 85 weeks
and 15 weeks respectively, could not only walk on a treadmill, they
could walk on a regular surface assisted by a walker or horizontal
poles to compensate for their residual balance problems.
All four were able to stand independently with a walker and regained
trunk stability.
They lost those abilities as soon as the stimulator was turned off.
Dr. Harkema, who is with the university's Kentucky Spinal Cord
Injury Research Center, said one problem is that the electronic
stimulator was never designed for this purpose, so it is difficult
to adjust on the fly to find the correct frequencies and intensities
to sensitize patients to the faint signals coming from the brain.
Medtronic, which makes the stimulator to combat pain, provided the
equipment, but no additional support.
The technique does not work in people whose spinal cords have been
completely severed, she said.
SOURCE: https://bit.ly/2NvZRGn The New England Journal of Medicine,
online September 24, 2018
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