ROSSLYN, Va., March 6, 2000---Biomedical engineers have developed a prototype neuroprosthesis that a quadriplegic can use to grasp and manipulate objects just by thinking about it.
The experimental device combines muscle-stimulating electrodes implanted under the skin with a computer sensitive to brain waves. Brain signals activate the electrodes that cause the hand muscles to contract.
This research goes back 20 years for Hunter Peckham, Ph.D., professor of biomedical engineering at Case Western Reserve University and director of the Functional Electrical Stimulation Center, a consortium of the Cleveland VA Medical Center, Case Western and MetroHealth Medical Center.
The work of Peckham and his colleagues has resulted in the first Food and Drug Administration-approved neuroprosthesis that uses electrodes implanted under the skin to give patients the ability to manipulate their paralyzed limbs.
The device, called the Freehand System, was licensed by Case Western to a private start-up company, NeuroControl. The Freehand System is operated by a joystick-like device worn under the clothing. The patient moves the joystick with the opposite shoulder. The joystick activates implanted electrodes that stimulate muscles to open and close the hand. More than 150 patients are using the system.
Now Peckham's laboratory is experimenting with other control devices. Clinical trials are under way on a system that uses an implanted sensor at the wrist to control muscle stimulation. It also enables patients to reach overhead.
Another system in earlier stages of development is one that uses brain activity as detected by an electroencephalogram to control the neuroprosthesis.
The new prototype, which has only been tested in the laboratory, couples an advanced, Freehand-like system with a monitor sensitive to brain waves. The monitor is worn like a shower cap dotted with electrodes. Wires lead from the electrodes to a computer that converts the brain signals into signals that open and close the hand.
Jim Jatich, 51, of Akron, Ohio, a quadriplegic injured in a diving accident 20 years ago, has tested the system with some encouraging results. He gained mental control of the device after a series of training sessions in which he learned to regulate his beta-rhythm through biofeedback.
During the training, Jatich learned to move a cursor up or down on a computer screen just by thinking about it. Then he was connected to the neuroprosthesis. By thinking about moving the cursor up, he opened his hand, and by thinking "down," his hand closed. He can use the device to pick up objects like a drinking glass and a fork.
"Now if I think open, my hand just opens," Jatich said. "It's just weird. But I have to keep thinking open, open, open. If I think of anything else I lose control. So there's a switch that locks my hand in the open or closed position."
"We just have to get rid of the cap, and that's the next step. Then we'd have a totally implanted system under the scalp, and that would also produce a better signal," Jatich said.
Peckham's group is also evaluating whether the brain signals will be sufficient to give Freehand users the full range of motion now available with the conventional device.