Electrode implants offer new hope for paralysis patients

Results from experiments on cat implanted with a tiny array of electrodes have offered new hope for patients with spinal cord injuries to control their paralyzed arms and legs.

When a patient is paralyzed, one of the possible causes is damage to the spinal cord, which along with the brain makes up the central nervous system. The brain is working, and so are motor and sensory nerves in the peripheral nervous system, but electrical signals can't flow between those nerves and the brain.

To address the communication problem, V. John Mathews, professor of electrical engineering and computer science in the Oregon State University (OSU) College of Engineering, lead researcher Mitch Frankel, then a Ph.D. student at the University of Utah, and three other researchers, all faculty members at Utah, conducted experiments that involved transmitting precisely controlled electrical pulses into nerves activating plantar-flexor muscles in an ankle of an anesthetized cat.

Using an optimized proportional-integral-velocity (PIV) controller, the researchers sent the pulses and the cat's nerves received them via a 100-electrode array whose base measured just 16 square millimeters. Thanks to specific electrodes being able to activate the right nerve fibers at the right times, the controller made the cat's ankle muscles work in a smooth, fatigue-resistant way.

The results, published in the journal Frontiers in Neuroscience, suggest that someday a paralyzed person might be equipped with a wearable, smartphone-sized control box that would deliver impulses to implanted electrodes in his or her peripheral nervous system, thus enabling at least some level of movement.

"Say someone is paralyzed and lies in bed all day and gets bed sores," Mathews was quoted as saying in a news release from OSU. "Early versions of this technology could be used to help the person get up, use a walker and make a few steps. Even those kinds of things would have an enormous impact on someone's life, and of course we'd like people to do more. My hope is in five or 10 years there will be at least elemental versions of this for paralyzed persons."

While the study focused on helping the paralyzed, a related research area involves amputees: neuroprostheses that can be controlled by thought based on decoding what goes on electrically inside a person's brain when he or she wants to, for example, move his or her arm or leg. "We can learn from the brain what the intent is and then produce the signals to make the movement happen," Mathews said. Endit