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 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."
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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."
(Editing by Michele Gershberg and Douglas Royalty)
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