THURSDAY, Nov. 29, 2012 (HealthDay News) -- Noninvasive stimulation of nerves in the brain and wrist may temporarily improve hand movement in people with partial spinal cord injuries, an early study suggests.
The study, published Nov. 29 in the journal Current Biology, involved just 19 people with spinal cord injuries that had partially damaged their ability to move and feel their arms and hands. And it looked only at the short-term effects of the nerve stimulation technique.
But researchers say the findings are a step toward helping people regain better use of their hands after such injuries.
If further work pans out, they envision developing portable devices that people could use at home to stimulate nerves and promote longer-lasting improvements in their muscle function.
"But we're still far from that goal," cautioned Monica Perez, study co-author and an assistant professor of physical medicine and rehabilitation at the University of Pittsburgh School of Medicine.
Before the technique is used as an actual therapy, the researchers need to know if it can lead to lasting changes in hand function.
"We're trying to understand the mechanisms of this plasticity, and how we can make these changes more permanent," Perez said.
More than half of people who survive spinal cord injuries are left with damage to the cervical spine, the upper portion of the spinal cord. And that often causes impairments in the hands and arms, Perez noted.
For the current study, she and University of Pittsburgh colleague Karen Bunday paired two forms of noninvasive nerve stimulation. The first was electrical stimulation of the ulnar nerve in the wrist. The other was transcranial magnetic stimulation, where an electromagnetic coil is placed near the scalp to create electric currents that stimulate targeted nerve cells -- in this case, in the part of the brain connected to hand function.
The researchers tested the combination's effects on 19 people with cervical spinal cord injuries and 14 healthy people. Each participant received 100 paired electrical pulses over about 20 minutes.
Perez and Bunday found that when they precisely timed the stimulation of the brain and wrist nerves, temporary improvements occurred in the injured participants' hand muscle strength and their ability to grasp and move small pegs.
The effects lasted up to 80 minutes.
Other stimulation techniques are currently under study to help people recover from spinal cord injuries. Some are invasive: Last year, researchers at the University of Louisville in Kentucky reported in The Lancet that electrodes implanted along the spine had helped a paralyzed 25-year-old man learn to walk again.
The tactic used in the new study combines noninvasive nerve stimulation approaches and focuses on timing.
The researchers found that electrical pulses from the brain needed to be precisely timed to arrive at the spinal cord one to two milliseconds before pulses from the wrist nerve did. And to do that, the stimulation needed to be individualized for each study participant.
In the future, it might be possible to use the approach in formal rehab programs for people with partial spinal cord injuries -- or even create at-home devices that would do the job, according to Perez.
Dr. Robert Grossman, chairman of neurosurgery at the Methodist Neurological Institute in Houston, agreed that there is potential for this technique to "enhance the rehabilitation" of some patients. He was not associated with the study.
He said the findings confirm previous research suggesting benefits from "raising the excitability of motor neurons" -- spinal nerve cells that send impulses to muscle.
Like Perez, Grossman urged caution in interpreting the findings of an early study. But he said the work is encouraging.
"Scientists are making slow but steady progress toward helping [spinal cord injury] patients recover some of their function," Grossman said.
Learn more about spinal cord injuries from the U.S. National Institute of Neurological Disorders and Stroke.