Revolutionary implant helps paralysed patients walk again
A
small group of paraplegic patients have once again been able to take
steps after researchers implanted a device to electrically stimulate
their spinal cords.
Two
separate teams of scientists have revealed for the first time that the
technique, together with physical training, has allowed three out of the
five individuals treated to walk again after losing all voluntary
movement below the site of the injury.
“It
is incredible to be able to be in there and actually see them taking
their first steps,” said Dr Claudia Angeli of Kentucky Spinal Cord
Injury Research Centre at the University of Louisville, and a co-author
of one of the studies.
“It
is an emotional time for the individual [themselves] because it is
something that they have been told they are never going to be able to do
again.”
In a study published in the New England Journal of Medicine,
Angeli and colleagues report that they implanted an array of 16
electrodes in the lower back of four patients, paralysed after mountain
bike or traffic accidents several years before.
The
device, originally developed many years ago for pain control, was
placed below the site of injury, covering regions that send sensorimotor
signals to the legs while a battery was implanted in the abdominal
wall, allowing the frequency of the stimulation, its intensity and
duration, to be tweaked wirelessly.
The
approach – called epidural stimulation – works on the principle that
there are still some small signals from the brain that cross the site of
the spinal cord injury – even though these are not enough on their own
to generate voluntary movement.
“We know the spinal cord has the ability to organise very detailed motor activity,” said Angeli.
“But before the injury it was getting commands from the brain and it was getting information from the environment as well.”
The injury, she said, disrupts this.
“The
spinal cord is isolated, it potentially still receives information from
the environment, but it is losing the big driver, which was the brain.”
Angeli
said that it is thought that when the implanted device is turned on,
the resulting electrical stimulation raises the excitability of the
spinal cord – in a sense making it more alert.
“It
is like it is more aware, it actually can listen to that little whisper
from the brain that is still there and it can generate the motor
pattern,” said Angeli, adding that training to link movements with these
signals is crucial.
All four of the individuals had lost all motor control below the site of the injury, although two had some level of sensation.
After implantation of the device and locomotor training, the latter two were eventually able to walk over ground unassisted.
One
was able to walk after 81 sessions of stimulation over 15 weeks,
although she had to use a walking frame, while the other was able to
walk after 278 sessions over 85 weeks, requiring either parallel bars or
holding people’s hands. In total he was able to walk just over 90
metres without a break.
The
other two individuals became able to stand and sit independently and
one was also able to make some stepping motions on a treadmill when
supported – however the other sustained a spontaneous hip fracture after
one week of training and only began training again a year later.
A separate paper by researchers from the Mayo clinic in Minnesota and UCLA, published in the journal Nature Medicine, also reports success with the same approach.
The
team revealed that after 43 weeks of training with the implant a
29-year-old man, paralysed after a snowmobile accident and left with no
sensation or voluntary motion below the injury, could walk without help
on a treadmill – holding on to the rails – and across the ground, albeit
with a moving frame and a little human help to maintain balance. He did
not, however, regain sensation in his legs.
Professor
Gregoire Courtine from the EPFL research institute in Switzerland, who
was not involved in either study, said he welcomed the research. But he
said a key problem was that the current applied to the electrodes was
continuous, meaning it can only be of low intensity – which may not
result in the “whisper” from the brain being heard loudly enough by the
legs.
Courtine
said he is working to solve this issue by synchronising the electrical
stimulation with intended movements – his previous work in monkeys used
brain implants to pick up on movement signals from the brain and send
them to the legs, bypassing the site of injury and allowing a greater
amplification of the signal to produce more robust muscle activity.
Mike
Milner, CEO of the Nicholls Spinal Injury Foundation was also cautious,
saying while the research looked promising, the charity supports
another approach to tackle spinal injury using special cells taken from a
patient’s nose, as well as nerve fibres, to patch the site of the
injury.
“We are looking for not only a natural, or biological, cure for paralysis – but a permanent one,” he said.