NEW YORK: Four men who had each been paralyzed from the chest down for
more than two years and been told their situation was hopeless regained
the ability to voluntarily move their legs and feet, though not to walk,
after an electrical device was implanted in their spines, researchers
reported on Tuesday.
The success, albeit in a small number of
patients, offers hope that a fundamentally new treatment can help many
of the 6 million paralyzed Americans, including the 1.3 million with
spinal cord injuries. Even those whose cases are deemed so hopeless they
are not offered further rehabilitation might benefit, scientists say.
The results also cast doubt on a key assumption about spinal cord
injury: that treatment requires damaged neurons to regrow or be replaced
with, for instance, stem cells. Both approaches have proved fiendishly
difficult and, in the case of stem cells, controversial.
"The
big message here is that people with spinal cord injury of the type
these men had no longer need to think they have a lifelong sentence of
paralysis," Dr Roderic Pettigrew, director of the National Institute of
Biomedical Imaging and Bioengineering, part of the National Institutes
of Health, said in an interview. "They can achieve some level of
voluntary function," which he called "a milestone" in spinal cord injury
research. His institute partly funded the study, which was published in
the journal Brain.
The partial recovery achieved by "hopeless"
patients suggests that physicians and rehabilitation therapists may be
giving up on millions of paralyzed people. That's because physical
therapy can mimic some aspects of the electrical stimulation that the
device provided, said Susan Harkema, a specialist in neurological rehab
at the University of Louisville's Kentucky Spinal Cord Injury Research
Center (KSCIRC), who led the new study.
"One of the things this
research shows is that there is more potential for spinal cord injury
patients to recover even without this electrical stimulation," she said
in an interview. "Today, patients are not given rehab because they are
not considered 'good investments.' We should rethink what they're
offered, because rehabilitation can drive recovery for many more than
are receiving it."
BASEBALL STAR
The
research built on the case of a single paralyzed patient that Harkema's
team reported in 2011. College baseball star Rob Summers had been
injured in a hit-and-run accident in 2006, paralyzing him below the
neck.
In late 2009, Summers received the epidural implant just
below the damaged area. The 2.5-ounce (72-gram) device began emitting
electrical current at varying frequencies and intensities, stimulating
dense bundles of neurons in the spinal cord. Three days later he stood
on his own. In 2010 he took his first tentative steps.
His
partial recovery became a media sensation, but even the Louisville team
thought that epidural stimulation could benefit only spinal cord
patients who had some sensation in their paralyzed limbs, as Summers
did. "We assumed that the surviving sensory pathways were crucial for
this recovery," Harkema said.
She and her team had little hope for two of their next patients. Neither had sensation in their paralyzed legs.
One was Kent Stephenson, who had been paralyzed in a 2009 motocross
crash when he was 21. After months of rehab in Colorado, "they said I
would never move my legs again, and there was no hope," he said.
Eleven days after he began receiving the deck-of-cards-size
RestoreAdvanced stimulator, which is made by Medtronic and used for pain
control, Stephenson moved his "paralyzed" left leg while lying on his
back.
"My mom, who was in the room when they turned the
stimulator on and told me, 'Pull your left leg up,' cried when I did
it," Stephenson said. "I got a little watery-eyed, too. I'd been told
I'd never move voluntarily again."
The researchers didn't
expect him to, either, said Claudia Angeli of the Frazier Rehab
Institute and KSCIRC, who co-led the study: "So when Kent moved, we
thought, huh, this might actually be working."
Andrew Meas,
whose head-on collision with a car while he was riding home on his
motorcycle in 2006 left him paralyzed from the chest down, made even
more progress. He can move even when the stimulator is not emitting
electrical signals.
The first time he was able to move his legs
"it made me feel like a normal person again," he said. After months of
rehab post-implant, "I can pick up both my legs without the stimulator
on, and can also stand without it. My record is 27 minutes, and I'm
still progressing."
At first, Meas could move his legs only
when the implant's 16 electrodes were zapping their spinal neurons at
full power. Over 28 weeks of daily physical therapy, he gradually became
able to move his toes, feet, ankles, knees, legs and hips with less
electrical stimulation.
ELECTRICAL BARRAGE
Meas's experience offers clues to how epidural stimulation works in
patients with spinal cord injury. Just as continuous exposure to an
allergen can eventually make people so sensitized that they sneeze and
wheeze at a single grain of pollen, so the electrical barrage "resets
the level of excitability of spinal cord neurons," said NIH's Pettigrew.
As a result, "even input from exercise could be enough to trigger a
motor response."
In addition to regaining voluntary movement,
the patients put on muscle mass and felt less tired and generally
happier. Summers is coaching baseball. Stephenson goes whitewater
rafting and motocrossing in a sidecar.
Even researchers who
have pioneered competing approaches, using cells, praised the new work.
"It's not a cure," said Dr Barth Green, a neurosurgeon at the University
of Miami, whose Miami Project to Cure Paralysis is trying to treat
spinal cord patients with cell transplants. "But it could be part of a
combined biological and bioengineering strategy to help patients not
just walk again but also gain control of their bowel and bladder," which
many paralyzed patients identify as even more important to their
quality of life.
The Louisville researchers suspect that with
better stimulator technology, spinal cord patients will be able to "work
toward stepping," as they carefully phrase it to avoid the hype
associated with "walking again." The electrodes in the current device
must either be all on or all off, for instance; alternately stimulating
the left and right sides might be more effective.
The
bioengineering institute at NIH is funding research to develop
noninvasive stimulators. That way, the electrical pulses can be
delivered through the skin rather than requiring surgery to implant a
device, Pettigrew said.
Even in patients with severe spinal
cord injuries, and even after experts have pronounced them incapable of
recovery, "we believe there is still a capacity for recovery," Harkema
said. "It's not necessarily the case that you will never move again."
