A new way of electrically
stimulating the spinal cord with wireless implants, together with therapy that
supports body weight, has helped three men with paraplegia to walk again with
the help of walking frames and crutches. They can even take a few steps without
any aids at all.
A new technique has enabled men with paraplegia
to walk again using walking frames.
Many years previously, the three men
sustained injuries in the cervical area, or neck region, of their spinal cords
that had left them paralyzed in their lower bodies.
The new "therapeutic
framework" responsible for their rehabilitation is called Stimulation
Movement Overground (STIMO).
It is the result of a collaboration
between Ecole Polytechnique Fédérale de Lausanne (EPFL) and the Lausanne
University Hospital (CHUV), both in Switzerland.
Two journals, Nature and Nature Neuroscience, have now published study
papers about the new stimulation approach.
What is
remarkable about the new method — and distinguishes it from two recently
published studies from the United States on a similar topic — is that the men
could move their legs when the electrical stimulation to the spinal cord was
switched off.
In one of the study papers, the
researchers explain the importance of "preserving proprioception" in
order to restore movement control in humans with spinal cord injury.
The need
to 'preserve proprioception'
Proprioception is the ability to
sense bodily position and movement by processing signals that come from the
body itself, as opposed to its environment. Scientists often describe it as a
"sixth sense."
Some who have written about it
have cited the
example of a man who, despite being able to make his muscles
contract, was effectively immobile after an "infection deprived him of the
sense of position, movement, and touch in his body" — or his
proprioception.
The
researchers in Switzerland maintain that if electrical stimulation of the
spinal cord does not have the right combination of precise location targeting
and timing of pulses, it can interfere with proprioception.
The STIMO method can overcome this
by using "burst stimulation and spatiotemporal stimulation profiles."
Using simulations, the researchers showed that it enabled "robust control
over motor neuron activity."
"The exact timing and location
of the electrical stimulation," explains co-author Jocelyne Bloch, a
professor and neurosurgeon at CHUV, who carried out the implant surgery,
"are crucial to a patient's ability to produce an intended movement."
Swiss
watch precision
Senior study author Prof. Grégoire
Courtine, a neuroscientist at EPFL, notes that, following years of researching
animal models, they "were able to mimic in real time how the brain
naturally activates the spinal cord."
He suggests that the precise
combination of location and timing of the impulses is what helped generate new
nerve connections.
Prof. Bloch says that it has to be
"as precise as a Swiss watch." The implants consist of a series of
electrodes that target specific groups of leg muscles.
"Selected configurations of
electrodes are activating specific regions of the spinal cord, mimicking the
signals that the brain would deliver to produce walking," she adds.
The three men had to learn how to
time their intention to walk with the stimulation pulses. After only 1 week of
this "calibration" phase, all three were walking with
"body-weight support."
"All the patients could walk using body-weight support
within 1 week. I knew immediately that we were on the right path."
Prof.
Jocelyne Bloch
Within 5 months, their
"voluntary muscle control improved tremendously," says Prof.
Courtine. "The human nervous system responded even more profoundly to the
treatment than we expected."
The men showed no fatigue in
their leg muscles and were walking hands-free for more than a kilometer during
their rehabilitation sessions.
'Activity-dependent
plasticity'
The intense and lengthy sessions
helped the men's nervous systems to trigger "activity-dependent
plasticity" and reorganize nerve fibers. This is what led to improved
movement ability, even in the absence of stimulation.
The team now wants to translate the
findings into tailored treatments that can be used in hospitals and clinics.
The scientists are also now
developing "next-generation neurotechnology," which they hope to test
soon after injury when there is a greater chance of recovery because the
affected tissue has not started to die off.
According to estimates from the
National Spinal Cord Injury Statistical Center at the University of Alabama at
Birmingham, there are about 288,000 people living with spinal cord injury in the U.S.
Every year, medical professionals diagnose around 17,700 new cases, of which 78
percent are in males.
Injury incurred during vehicle
crashes account for most (38 percent) cases of spinal cord damage in the U.S.,
followed by falls (32 percent). Other relatively common causes include wounding
from gunshots and other violent acts (14 percent), together with injuries that
occur during sports or recreation (8 percent).
The following video from EPFL
summarizes the research and illustrates the progress that the three men made
during their rehabilitation.
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